Discovery Could Rewrite History of Vikings in New World

Guided by ancient Norse sagas and modern satellite images, searchers discover what may be North America's second Viking site.

It’s a two-mile trudge through forested, swampy ground to reach Point Rosee, a narrow, windswept peninsula stretching from southern Newfoundland into the Gulf of St. Lawrence. Last June, a team of archaeologists was drawn to this remote part of Canada by a modern-day treasure map: satellite imagery revealing ground features that could be evidence of past human activity.

The treasure they discovered here—a stone hearth used for working iron—could rewrite the early history of North America and aid the search for lost Viking settlements described in Norse sagas centuries ago.

To date, the only confirmed Viking site in the New World is L’Anse aux Meadows, a thousand-year-old way station discovered in 1960 on the northern tip of Newfoundland. It was a temporary settlement, abandoned after just a few years, and archaeologists have spent the past half-century searching for elusive signs of other Norse expeditions.

“The sagas suggest a short period of activity and a very brief and failed colonization attempt,” says Douglas Bolender, an archaeologist specializing in Norse settlements. “L’Anse aux Meadows fits well with that story but is only one site. Point Rosee could reinforce that story or completely change it if the dating is different from L’Anse aux Meadows. We could end up with a much longer period of Norse activity in the New World.”

The site of the discovery, hundreds of miles south of L’Anse aux Meadows, was located by archaeologist Sarah Parcak, a National Geographic Fellow and “space archaeologist” who has used satellite imagery to locate lost Egyptian cities, temples, and tombs.

Last November, TED awarded Parcak a $1 million prize to develop a project to discover and monitor ancient sites. This latest discovery in Newfoundland—supported, in part, by a grant from the National Geographic Society—demonstrates that her space-based surveillance can not only spy out artifacts in barren desert landscapes, but also in regions covered by tall grasses and other plant life.

Parcak led a team of archaeologists to Point Rosee last summer to conduct a “test excavation,” a small-scale dig to search for initial evidence that the site merits further study. The scientists unearthed an iron-working hearth partially surrounded by the remains of what appears to have been a turf wall.

The archaeologists don’t yet have enough evidence to confirm that Vikings built the hearth. Other peoples lived in Newfoundland centuries ago, including Native Americans and Basque fisherman. But experts are cautiously optimistic.

“A site like Point Rosee has the potential to reveal what that initial wave of Norse colonization looked like not only for Newfoundland but for the rest of the North Atlantic,” says Bolender.

Location, Location, Location

“Who’s your daddy?!?” Parcak shouts at the ground as her muddy boot pushes down on a shovel, cutting its way through thick turf to the soil beneath. It’s a joyous sound, the primal yell of an archaeologist in her natural habitat, doing fieldwork. “Digging makes us better people,” she tells me.

Parcak is far afield of her usual stomping grounds in Egypt. But this project has clearly captivated her imagination, drawing her into Viking history and lore.

One afternoon, we cautiously make our way down a steep path—created by a small landslide and gully—to a narrow beach. As we stroll along the shoreline, Parcak speculates on why this tiny peninsula would have made an ideal Norse outpost.

“They were quite nervous about their safety, threats by locals,” she says. “They needed to be in a place where they could have good access to the beaches but also a good vantage point. This spot is ideally situated—you can see to the north, west, and south.”

After studying the area and researching prior land surveys, the archaeologists have identified other characteristics that would have made Point Rosee an optimum site for Norse settlers: The southern coastline of the peninsula has relatively few submerged rocks, allowing for anchoring or even beaching ships; the climate and soil in the region is especially well-suited for growing crops; there’s ample fishing on the coast and game animals inland; and there are lots of useful natural resources, such as chert for making stone tools and turf for building housing.

Iron Men

And then, of course, there was the most valuable resource of all: bog iron. It’s a type of ore that forms when rivers carry dissolved particles of iron down from mountains and into wetlands, where bacteria leach the iron from the water, leaving behind metal deposits.

The Norse didn’t do much mining. Most of their iron was harvested from peat bogs, and their very way of life depended upon it. Metal nails held their ships together as they sailed west—expanding their realm across the North Atlantic—and south, establishing trade routes throughout Europe and the Far East. A modern-day reconstruction of a Norse longship, built by the Viking Ship Museum in Denmark, required 7,000 nails made from 880 pounds (400 kg) of iron—which means that a blacksmith would have had to heat and process 30 tons of raw bog iron ore.

Bog iron prospectors knew what telltale signs to look for, such as an oily looking microbial slick on the surface of stagnant water. In fact, three historians authored a study making the case that iron was a prerequisite for Viking settlements. L’Anse aux Meadows, they observe, was a site used for iron production and ship maintenance, providing evidence “that the explorers, knowing their ships needed repair, actively sought out a location where they could acquire bog iron and produce new nails.”

Searching For Signs

Up until now, Parcak has predominantly used her eyes in the sky to gaze upon Egypt, where she has been able to spot geological anomalies that indicate the presence of ruins beneath the barren, mostly undisturbed sands.

But, whereas the ancient Egyptians left behind stone edifices that have endured for thousands of years, Viking structures were hewn mostly from wood and earth. So when Parcak uses satellite imagery to search for signs of Norse settlers, she’s not looking for actual ruins. Instead, she’s scrutinizing the plant life.

The remnants of structures buried at Point Rosee alter the surrounding soil, changing the amount of moisture it retains. This, in turn, affects the vegetation growing directly over it. Using remote sensing, variations in plant growth form a spectral outline of what was there centuries earlier. The Point Rosee images were taken during the fall, when the grasses in the area were particularly high, making it easier to see which plants were healthier, drinking more water from the soil.

In one area, a magnetometer survey reveals a hot spot that, according to the satellite imagery, is partially surrounded by straight lines indicating the possible ruins of a small structure. Excavation reveals the remains of what appear to be turf walls and an iron-working hearth.

To an untrained eye, the hearth doesn’t look like much: a boulder in front of a shallow pit, surrounded by smaller stones. But traces of charcoal and 28 pounds of slag found in the pit suggest to the archaeologists that this hearth was used for roasting ore.

This was the first step in the iron-working process. Before the metal could be smelted and forged by a blacksmith, the ore needed to be dried out—otherwise, it would explode when placed inside a furnace. The roasting process also removed some of the impurities, in the form of discarded metal slag.

The discovery of this hearth makes Point Rosee the southernmost and westernmost known iron-working site in pre-Columbian North America.

The Stuff of Legends

Was Point Rosee a Viking outpost a thousand or so years ago? The evidence thus far is promising. The turf structure that partially surrounds the hearth is nothing like the shelters built by indigenous peoples who lived in Newfoundland at the time, nor by Basque fishermen and whalers who arrived in the 16th century. And, while iron slag may be fairly generic, “there aren’t any known cultures—prehistoric or modern—that would have been mining and roasting bog iron ore in Newfoundland other than the Norse,” says Bolender.

Very few artifacts have been found at Point Rosee, but that’s actually a good sign. Most Norse possessions haven’t preserved well; they were typically made from wood, which decayed, or iron, which either decayed or was melted down to make something else. Archaeologists conducted seven excavations at L’Anse aux Meadows, from 1961 to 1968, before they had sufficient evidence to confirm it was a Norse outpost. And even then they found only a handful of personal items, such as a bronze pin, a needle hone, and a stone lamp. If the archaeologists had found many artifacts at Point Rosee, then it probably wouldn’t be a Viking site.

One theory is that Point Rosee was primarily an iron-working camp, a temporary facility supporting exploration and exploitation of resources within the Gulf of St. Lawrence. Bolender, however, believes it might have been part of a more substantial settlement somewhere in the vicinity.

If so, then how does this discovery fit into history’s bigger picture?

Much of what we know about the Norse exploration of North America is gleaned from the Viking sagas, oral stories passed down across generations that were eventually transcribed.

“We’re looking here because of the sagas,” says Bolender. “Nobody would have ever found L’Anse aux Meadows if it weren’t for the sagas. But, the flipside is that we have no idea how reliable they are.” Archaeologists have found sporadic evidence suggestive of Viking explorers who traveled beyond their settlements in Greenland. Artifacts from the 11th century, including a copper coin, were discovered in Maine, possibly obtained by Native Americans who traded with the Norse. Canadian archaeologist Patricia Sutherland has found ruins on Baffin Island, far above the Arctic Circle, which she claims were a trading outpost—though the evidence remains inconclusive. (Read about Sutherland’s discovery.)

The confirmed discovery of a Norse camp at L’Anse aux Meadows proved that the Viking sagas weren’t entirely fiction. A second settlement at Point Rosee would suggest that the Norse exploration of the region wasn’t a limited undertaking, and that archaeologists should expand their search for evidence of other settlements, built 500 years before the arrival of Christopher Columbus.

“For a long time, serious North Atlantic archaeologists have largely ignored the idea of looking for Norse sites in coastal Canada because there was no real method for doing so,” says Bolender. “If Sarah Parcak can find one Norse site using satellites, then there’s a reasonable chance that you can use the same method to find more, if they exist. If Point Rosee is Norse, it may open up coastal Canada to a whole new era of research.”
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Reference:

Strauss, Mark. 2016. “Discovery Could Rewrite History of Vikings in New World”. National Geographic News. Posted: March 31, 2016. Available online: http://news.nationalgeographic.com/2016/03/160331-viking-discovery-north-america-canada-archaeology/

Ancient ring brings Vikings and Islamic civilizations closer together

A glass ring found in a Viking grave belonging to a Swedish woman offers proof that Vikings were in direct contact with the ancient Islamic civilizations.

The ring, which is decorated with glass and not amethyst as previously assumed, has an inscription that reads ”to Allah” or “for Allah” in Arabic, writes ScienceNews.

According to the archeologists behind the discovery, it’s a well-established fact that Scandinavians traded for glass with people from Egypt and Mesopotamia as far back as 3,400 years ago -- so it’s not that unlikely to think that seafaring Vikings might’ve taken the trip down there themselves and traded with the Islamic merchants in the region, says the researchers from Stockholm University.

The researchers used a scanning electron microscope to determine which material the ring was made of and to read the inscription.

Proves trade between Vikings and Muslims

The researchers write in their article, which was recently published in the journal Scannin, that the ring could constitute proof of direct interactions between Vikings and the Islamic civilisations.

”Being the only ring with an Arabic inscription found at a Scandinavian archaeological site, it is a unique object among Swedish Viking Age material,” they write.

According to Jeanette Varberg, director of Moesgaard Museum in Denmark, it’s a very exciting discovery. However, she says she’s not surprised that there were direct trade routes connecting ancient Scandinavia with the East.

“It underlines that Birka has been the gate to the East,” says Varberg to ScienceNordic. “It’s clear that there used to be trade routes across the Mediterranean.”
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Reference:

Persson, Charlotte Price. 2015. “Ancient ring brings Vikings and Islamic civilizations closer together”. Science Nordic. Posted: March 19, 2015. Available online: http://sciencenordic.com/ancient-ring-brings-vikings-and-islamic-civilizations-closer-together

Norwegian Vikings Purchased Silk from Persia

The Norwegian Vikings were more oriented towards the East than we have previously assumed, says Marianne Vedeler, Associate Professor at the Museum of Cultural History, University of Oslo in Norway. After four years of in-depth investigation of the silk trade of the Viking Age, she may change our perceptions of the history of the Norwegian Vikings. The silk trade was far more comprehensive than we have hitherto assumed.

The Norwegian Vikings maintained trade connections with Persia and the Byzantine Empire. A network of traders from a variety of places and cultures brought the silk to the Nordic countries. Her details are presented in the book "Silk for the Vikings," to be published by Oxbow publishers this winter, but in this article you can glimpse some of her key findings.

In the Oseberg ship, which was excavated nearly a hundred years ago, more than one hundred small silk fragments were found. This is the oldest find of Viking Age silk in Norway.

At the time when the Oseberg silk was discovered, nobody conceived that it could have been imported from Persia. It was generally believed that most of it had been looted from churches and monasteries in England and Ireland.

Lots of Viking silk

Since the Oseberg excavation, silk from the Viking Age has been found in several locations in the Nordic countries. The last finding was made two years ago at Ness in Hamarøy municipality, Nordland county. Other Norwegian findings of silk from the Viking Age include Gokstad in Vestfold county, Sandanger in the Sunnmøre district and Nedre Haugen in Østfold county.

The highest number of burial sites containing silk from the Viking Age have been found at Birka in the Uppland region, a few miles west of Stockholm.

"Even though Birka has the highest number of burial sites containing silk, there are no other places where so much and such varied silk has been found in a single burial site as in Oseberg," says Marianne Vedeler to the research magazine Apollon.

In Oseberg alone, silk from fifteen different textiles, as well as embroideries and tablet-woven silk and wool bands were discovered. Many of the silk pieces had been cut into thin strips and used for articles of clothing. The textiles had been imported, while the tablet-woven bands most likely were made locally from imported silk thread.

Marianne Vedeler has collected information on silk and its trade in the Nordic countries. She has also studied manuscripts on silk production and trade along the Russian rivers as well as in Byzantium and Persia.

"When seeing it all in its totality, it's more logical to assume that most of the silk was purchased in the East, rather than being looted from the British Isles."

Waterways

Vedeler believes that in the Viking Age, silk was imported from two main areas. One was Byzantium, meaning in and around Constantinople, or Miklagard, which was the Vikings' name for present-day Istanbul. The other large core area was Persia.

The silk may have been brought northwards along different routes.

One possibility is from the South through Central Europe and onwards to Norway, but I believe that most of the silk came by way of the Russian rivers Dnepr and Volga.

The Dnepr was the main route to Constantinople, while the Volga leads to the Caspian Sea. The river trade routes were extremely dangerous and difficult. One of the sources describes the laborious journey along the Dnepr to Constantinople:

"A band of traders joined up in Kiev. Along the river they were attacked by dangerous tribesmen. They needed to pass through rapids and cataracts. Then, slaves had to carry their boat."

Persian patterns

On the basis of the silk that has been found, there are indications that more silk came to Norway from Persia than from Constantinople.

Large amounts of the Oseberg silk have patterns from the Persian Empire. This silk is woven using a technique called samitum, a sophisticated Oriental weaving method. Many of the silk motifs can be linked to religious motifs from Central Asia.

Another pattern depicts a shahrokh, a bird that has a very specific meaning in Persian mythology; it represents a royal blessing. In the Persian myth, the shahrokh bird is the messenger that brings the blessing to a selected prince. In a dream, the bird visits the prince holding a tiara, a tall head adornment, in its beak. The prince then wakes up and knows that he is the chosen one. The image of the imperial bird was popular not only in silk weaving, but also in other art forms in Persia. The motif gained widespread popularity in Persian art.

It's an amusing paradox that silk textiles with such religious and mythological images were highly prized and used in heathen burial sites in the Nordic countries as well as in European churches.

Exclusive

In the Orient, silk was essential for symbolizing power and strength. There was an entire hierarchy of different silk qualities and patterns reserved for civil servants and royalty.

Even though silk was a prominent status symbol for the Vikings, they failed to get their hands on the best silk.

Most likely, the bulk of the silk imported to Scandinavia was of medium or below-medium quality.

In Byzantium, major restrictions were imposed on the sale of silk to foreign lands. The punishment for illegal sale of silk was draconian. The Persian lands also imposed strict restrictions on the sale and production of silk.

In Byzantium, it was illegal to buy more silk than what could be bought for the price of a horse. A foreign trader was allowed to buy silk for ten numismata, while the price of a horse was twelve numismata.

"However, several trade agreements that have been preserved show that traders from the North nevertheless had special trade privileges in Byzantium."

Silk was not only a trade commodity. Certain types of silk were reserved for diplomatic gifts to foreign countries, as described in Byzantine as well as Persian sources. In Europe, silk became especially popular for wrapping sacred relics in churches.

Some of the silk found in Norway may be gifts or spoils of war, but archaeological as well as written sources indicate that silk was traded in the Nordic countries.

"We may safely assume that the Vikings engaged in trade, plunder, exchange of gifts and diplomatic relations in equal measure."

A possible example of loot found in the Oseberg ship is a piece of silk with an image of a cross.

This was long before the introduction of Christianity. The silk piece may have been sewn locally, but it is also highly likely that it was purloined from an Irish church.

Possibly China

At Gokstad, thin strips of hammered gold wrapped around silk threads were among the findings. "These threads are highly exclusive. We do not know their origin, but we suspect that they may have come from even further east, in the direction of China," says Vedeler, who will now travel to China to find out more.

As yet, Vedeler must draw conclusions regarding the origin of the silk by investigating weaving technologies and patterns. With time, she wishes to make use of a new method which is being developed at the University of Copenhagen and which will be able to reveal the geographic origin of artefacts.
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References:

Science Daily. 2013. “Norwegian Vikings Purchased Silk from Persia”. Science Daily. . Posted: November 1, 2013. Available online: http://www.sciencedaily.com/releases/2013/11/131101091735.htm

Vikings May Have Been More Social Than Savage

Academics at Coventry University have uncovered complex social networks within age-old Icelandic sagas, which challenge the stereotypical image of Vikings as unworldly, violent savages.

Pádraig Mac Carron and Ralph Kenna from the University's Applied Mathematics Research Centre have carried out a detailed analysis of the relationships described in ancient Icelandic manuscripts to shed new light on Viking society.

In a study published in the European Physical Journal, Mac Carron and Kenna have asked whether remnants of reality could lurk within the pages of the documents in which Viking sagas were preserved.

They applied methods from statistical physics to social networks -- in which nodes (connection points) represent individuals and links represent interactions between them -- to home in on the relationships between the characters and societies depicted therein.

The academics used the Sagas of Icelanders -- a unique corpus of medieval literature from the period around the settlement of Iceland a thousand years ago -- as the basis for their investigation.

Although the historicity of these tales is often questioned, some believe they may contain fictionalised distortions of real societies, and Mac Carron's and Kenna's research bolsters this hypothesis.

They mapped out the interactions between over 1,500 characters that appear in 18 sagas including five particularly famous epic tales. Their analyses show, for example, that although an 'outlaw tale' has similar properties to other European heroic epics, and the 'family sagas' of Icelandic literature are quite distinct, the overall network of saga society is consistent with real social networks.

Moreover, although it is acknowledged that J. R. R. Tolkien was strongly influenced by Nordic literature, the Viking sagas have a different network structure to the Lord of the Rings and other works of fiction.

Professor Ralph Kenna from Coventry University's Applied Mathematics Research Centre said: "This quantitative investigation is very different to traditional approaches to comparative studies of ancient texts, which focus on qualitative aspects. Rather than individuals and events, the new approach looks at interactions and reveals new insights -- that the Icelandic sagas have similar properties to those of real-world social networks.
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References:

2013. “Vikings May Have Been More Social Than Savage”. Science Daily. Posted: October 1, 2013. Available online: http://www.sciencedaily.com/releases/2013/10/131001091338.htm

Old Arabic texts describe dirty Vikings

Arabs who encountered Scandinavians who had journeyed eastward depicted them as handsome people but filthy and barbaric.

They are the filthiest of all Allah’s creatures: they do not purify themselves after excreting or urinating or wash themselves when in a state of ritual impurity after coitus and do not even wash their hands after food.

The Arab writer Ahmad ibn Fadlan noted the above after meeting Viking travellers around a thousand years ago.

The Icelandic historian Thorir Jonsson Hraundal has studied comments about what we call Vikings in original texts by Arab historians and geographers. The texts described Arab encounters with Scandinavians in areas around the Caspian Sea and the Volga River.

Their depictions differ radically from images of fearsome Viking conquerors handed down from the British Isles and France in the same era.

Resilient Scandinavians

“A major difference between the Scandinavians who travelled eastwards and those who sailed west was that in the East they were far more subordinated in societies they came to,” says Jonsson Hraundal.

He recently presented his doctoral dissertation at the University of Bergen about the so-called Rus ― Scandinavian merchants and warriors who travelled to Eastern Europe, Central Asia and the Middle East.

“The Scandinavians appear to have been versatile people who were really good at adapting to diverse regions and participating in various power structures,” he says.

From the Nordic region to Baghdad

From the mid-800s until the ca. 1000 AD Scandinavians underwent something of a travel boom. The Vikings journeyed out into the world to explore, trade and battle. Norwegians are best acquainted with the raids in Western Europe and the voyages to Iceland, Greenland and North America.

According to Jonsson Hraundal it might have been nearly as common to head eastwards, using the major European rivers.

“Far more Scandinavian artefacts have been found in Eastern Europe than in the West, covering a much larger geographic area,” says the researcher.

The excursions in the direction of the sunrise were also extensive. A source studied by Jonsson Hraundal tells of Vikings who followed the European rivers down to the Caspian Sea and then crossed by boat and continuing to Bagdad on camel caravans.

It’s a distance of over 5,000 kilometres.

Visiting Turkish-ruled countries

Scandinavians were encountered in the eastern regions of the Continent for centuries. They were warriors, merchants and common labourers.

Some sources mention Vikings working as caravan guards – mercenary soldiers.

“Archaeological sources placed Vikings further west, but Arabs mainly confronted them closer to the Caspian Sea. This was a completely different cultural setting, one governed by Turks,” explains Jonsson Hraundal.

Turks are an ethnic group who include the people of modern Turkey, but many other peoples as well. Like Mongolians they descend from the Ural Altaic ethnic group.

“The Turks, and especially the Khazars and Bulgars, were the dominant powers in the region when the Rus arrived. The texts mainly show how powerful the Turks were. The Rus couldn’t just come in swinging their swords and take over,” says the historian.

Good looking, filthy and crazy

The aforementioned writer Ahmad ibn Fadlan was not fully repulsed by the Scandinavians he met:

I have never seen more perfect physiques than theirs – they are like palm trees, are fair and reddish, and do not wear the tunic or the caftan.

Ahmad ibn Fadlan describes funeral rites which generally conform to the Norse rituals of Scandinavia, but were very exotic for an Islamic intellectual:

In the case of a rich man, they gather together his possessions and divide them into three portions, one third for his household, one third with which to cut funeral garments for him, and one third with which they ferment alcohol which they drink on the day when his slave-girl kills herself and is burned together with her master.

Contemporary Arabic descriptions

It’s no news that the Vikings travelled eastwards. But archaeologists and historians have few sources detailing the travels. In Norway, for instance, written material about the journeys dates from long after the trips ended. This undermines the validity of the texts as historical source material.

The archaeologists have thus concentrated on artefacts from Byzantium, in present-day Turkey, and from Slavic areas such as Hungary.

“However, Muslim authors also travelled and met Scandinavian merchants. They made note of these episodes at the time they occurred,” says the historian Jonsson Hraundal.

This makes them excellent first-hand sources regarding the kind of people the Rus were.

Silver coins testify to contacts

For a number of reasons, the East-bound Vikings have been neglected by scholars in comparison to those who headed west. Political problems hampered Western archaeologists for decades. During much of the 20th century it was hard for West European researchers to access artefacts collected behind the Iron Curtain.

“We have a lot more source information from the West because of the linguistic and writing culture that dominated there,” adds Archaeology Professor Jan Bill of the University of Oslo.

“This doesn’t mean that the contact in the East was unimportant, but perhaps we haven’t had as much opportunity to study it.”

There are exceptions and Bill mentions that Arab silver coins and other artefacts from Kazakhstan and neighbouring areas have been found at Heimdalsjordet, a former marketplace not far from the Gokstad Viking Ship Mound in Sandefjord, southwest of Oslo.

“They come from the Silk Road and show that the Vikings definitely had contact with Islamic areas,” he says.

Deserving more emphasis

Another barrier is that the Arabic texts lack names for the Scandinavians they described, unlike many of the Western sources. The Arabs have evidently viewed them as a homogenous group, and haven’t considered the name of any incidental northern “infidel” relevant to the travel journals they wrote.

This makes the protagonists anonymous and for historians perhaps a little less enticing to study.

Jonsson Hraundal hopes his doctoral thesis can help open up more studies of what the Vikings did in the East.

“The Scandinavians who travelled eastwards are generally mentioned briefly in passing by textbooks and in school. I think this part of our history should be given much more attention,” he says.
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References:

Jakobsen, Hanne. 2013. “Old Arabic texts describe dirty Vikings”. Science Nordic. Posted: July 17, 2013. Available online: http://sciencenordic.com/old-arabic-texts-describe-dirty-vikings

Don’t underestimate Viking women

The status of Viking women may be underestimated due to the way we interpret burial findings.

“To assume that Viking men were ranked above women is to impose modern values on the past, which would be misleading,” cautions Marianne Moen. She has been studying how women’s status and power is expressed through Viking burial findings. Her master’s thesis The Gendered Landscape argues that viking gender roles may have been more complex than we assume.

Exploring new perspectives of Viking society is a theme which also will be the focus of the forthcoming Viking Worlds conference in March 2013, where Moen is a member of the organising committee.

Skewed interpretation

Our assumptions of gender roles in viking society could skew the way we interpret burial findings, Moen points out. She uses the 1904 excavation of the Oseberg long boat to illustrate the point. Rather than the skeleton of a powerful king or chieftain, the ship surprisingly contained two female skeletons.

“The first theories suggested that this must be the grave of queen Åsa mentioned in Snorri’s Ynglinga saga, and that the other skeleton was her slave servant,” says Moen. Åsa Haraldsdottir was the mother of Viking king Halfdan the Black.

However, later carbon dating revealed that the buried ship was from around 834 AD - a date which made this theory unfeasible. But the idea of a queen mother and her servant became persistent amongst archaeologists.

Powerful Oseberg women

”Since the Oseberg mound contained two women, the burial site has been analysed as a unique find, without reference to similar sites. The finding is very similar to the Gokstadskipet long boat, which is regarded as the grave of a powerful and influential king. So why isn’t Osebergskipet regarded in the same way?” asks Moen.

“There are several indicators that these women were powerful in their own right – but by defining one of them as a queen it is implied that her significance was due to who she was married to or had mothered.”

Using literary sources

And although we accept that some Viking women may have had a role as religious figures (as a ‘volve’) performing rites, we do not accord them the corresponding power they would have had in a society where religious and political power was intertwined, Moen argues.

“Our perception of religion’s influence in the society is based on texts written hundreds of years afterwards, by men from a different and more misogynistic religion.”

Moen feels many archaeologists have put too much emphasis on historical texts, such as Snorri Sturluson’s sagas.

“As archaeologists we have to base our analyses on archaeological material. Historical material do have some value, but only as secondary sources.”

Identifying male graves

The fact that far more graves of men than women have been found from this era has also been seen as an indication that men were more powerful. But it might not be that straightforward to identify a grave as male or female, Moen suggests.

Usually archaeologists have to rely on artefacts to gender identify a grave, due to a lack of human remains. But the presence of male objects (such as swords, shields or spears) or female objects (jewellery, fabric and weaving artefacts) does not conclusively prove the gender.

“There have also been cases of male graves with pearls and woven cloths, and women were sometimes buried with smaller weapons, for instance arrowheads. Generally it is fairly obvious what constitutes male or female objects, but the lines were sometimes blurred.”

Prominent female graves

Added to this, the larger metal objects usually found in male graves are more likely to be discovered after hundreds of years - while smaller female objects such as brooches (and hence, female graves) can remain undetected.

“If it is the case that women belonged to the private sphere of the home and men were in the public sphere of society, this should be reflected in the burial landscape,” Moen points out. But in the Kaupang area she has studied, female graves are side by side with male graves – and just as prominent.

Victorian ideals of domestic women

“Since the Viking era became an important part of building Norwegian national identity in the 19th century, early archaeology was influenced by Victorian ideals. The contemporary ideals of women belonging to the home and men being out in the public was imposed on Viking society,” says Moen.

“The domestic role of Viking women may have been less limited to the private sphere than it is today. The large estates were contemporary seats of power, and the woman of the house had the keys. How private or public this role was should be interpreted outside our own cultural context.”
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References:

Foss, Arild S. 2013. “Don’t underestimate Viking women”. Science Nordic. Posted: January 2, 2013. Available online: http://sciencenordic.com/don%E2%80%99t-underestimate-viking-women

How Vikings navigated the world

With no access to modern navigation instruments, Vikings relied on birds, whales, celestial bodies, chants and rhymes to navigate the seas and discover new land.

Today it seems like a bit of a mystery how our savage forefathers managed to navigate their way across the Atlantic centuries before Columbus discovered America.

Maybe it’s because they weren’t as dumb as some of us think. They understood how to link their travel stories and sensory impressions with observations of wind, weather, wildlife and solar time. This enabled them to figure out which way to go.

Experience helped Vikings understand nature

In order to understand the Vikings’ way of travelling, we need to rid ourselves of our current conception of nature and navigation:

“Back then, there were of course no compasses, echo sounders, satellite navigation or radio communication,” says Anton Englert, a PhD in archaeology who researches into Viking Age seafaring at the Viking Ship Museum in Roskilde, Denmark.

“The Vikings had an understanding of nature, since they lived in the wild. But their observations didn’t lead to any scientific data that they could use to construct precision tools.”

They knew of the concepts of east, west, south and north. But to them, navigation was more based on where on the horizon the sun rose and how high it was during the day, rather than Earth’s magnetism, which underlies the modern compass.

Vikings used landmarks and mental charts

The sun, the moon and the stars provided the Vikings with a decent understanding of which direction to travel.

But in fog and cloudy weather these celestial bodies are not visible, and on long stretches, a deviation of only a few degrees from the planned route can mean that you end up completely missing your intended destination.

For this reason, the Vikings also kept an eye on objects on land when they sailed along the coasts. A rock with a particular shape, for instance, or a hilltop, could provide some clues to where they were.

Chants and rhymes showed the way

Since there were neither nautical charts nor any written descriptions back then, the Vikings’ travelogues consisted of narratives and rhymes.

An example of these travelogues can be found the medieval Norse manuscript ’Hauksbók’:

"From Hernam [present-day Hennø near Bergen] in Norway, head due west towards Hvarf in Greenland, and you will have sailed north of Hjaltland [the Shetland Islands}, so that you just glimpse it in clear weather, but south of the Faroe Islands, so that the sea [the horizon] is right in between the distant mountains, and thus also south of Iceland.”

In other words: they sailed from Hennø in Norway, heading due west towards Greenland, between Shetland and the Faroes and south of Iceland.

Birds and whales served as navigation marks

When out sailing, the Vikings used wildlife as landmarks. Birds were particularly helpful, since some birds only flew a certain distance away from land.

If for instance they had long since passed the Faroes and saw a particular terrestrial bird, this could be a sign that they were near Iceland.

Whales usually stay close to currents where fish can be found. The Vikings knew where whales typically resided, and this knowledge helped them figure out where they were in relation to e.g. Iceland.

Vikings navigated with their senses

A common hypothesis in research circles is that Vikings used their senses to navigate. In addition to the obvious one – sight – they also made use of:

Hearing: The Vikings could hear how close they were to land when it was too foggy to see. They kept an ear out for the screeching of birds and the sound of waves breaking on the shore.

Touch: The sense of touch in our faces can be used to register changes in the speed and direction of the wind. This sensation can reveal differences between wind swells from various directions. And since nearby coasts can reflect swells back, a seasoned Viking could extract a lot of information just from a sea breeze.

Taste: One of the few navigation instruments the Vikings had at their disposal was a plumb bob, which they used for assessing the depth of the water. The plumb bob also collected a tiny sample of the seabed, which the men could then taste and touch. An experienced sailor could link the taste to other characteristics. It’s likely that the Vikings have been able to determine, using only their taste buds, if fresh water flowed from land into the sea water.

Smell: A seasoned mariner can smell whether or not he’s close to land. In humid conditions, the human nose is capable of detecting trees, plants and fire some distance from land.

Weather: an aid and an obstacle

Being the great seafarers that they were, the Vikings were probably great at observing weather patterns – for instance how a low pressure passed on a particular route. This helped them determine which direction to go.

Englert mentions an example of this:

“Your sails are filled with southern wind and rain, so that you’re sailing with the wind abeam from the board side towards the west. Your experience tells you that the rainy wind usually flows clockwise. To maintain the course on the high seas, the Vikings could then gradually trim the sails to keep them from luffing in periods when the sky was cloudy and neither the sun nor the stars were visible.”

Courage and poor soil lured Vikings across the Atlantic

Morten Ravn, who researches into Viking ships at Copenhagen University, mentions three possible explanations to what compelled the Vikings to go looking for new land as far out to sea as they did.

1.Coincidence: The Vikings’ navigation was far from accurate, which also explains why so many of their ships ended up on the bottom of the sea. But some of them found land and named it – for instance Iceland and Greenland.
2.Recognition and respect: It took courage to sail out and look for new land, and this gave prestige.
3.Lack of inheritance: A lack of inheritable land among the sons of farmers and magnates may have motivated them to find new land to conquer.

Anton Englert adds another possible explanation: banishment. He says that some of the sagas mention Norwegians who had become unpopular with the establishment at home. They went looking for places to settle down and enjoy their freedom.

The cold climate in the Faroes, Iceland and Greenland didn’t scare off the Vikings because it wasn’t much different from the Norwegian climate.

“Their familiarity with the North Atlantic climate and poor soil in Norway turned the Vikings into maritime people who looked for a better life on the other side of the ocean.”

America was discovered by chance

According to one historical source, Grænlendinga saga (The saga of the Greenlanders) America was discovered by accident in the autumn of 996 AD.

The saga tells the tale of Bjarni Herjólfsson, who is believed to be the first European to see North America when he set sail for Greenland to meet his father.

“Bjarni Herjólfsson had learnt how to sail to Greenland from Norway, but his ship encountered several days of strong northerly wind and fog,” explains Englert. “His ardent efforts to keep the ship afloat resulted in his ship being blown off course.”

The discoverer of America was mocked

In his efforts to get back on course, Bjarni Herjólfsson tried to sail due west again. He eventually saw a piece of land [North America], but this land was more fertile than the Greenland he had heard about.

His crew wanted to go ashore, but Herjólfsson insisted on reaching Greenland before the end of the sailing season. So he headed north and there he noticed that the land was becoming less fertile and rockier.

After a while he saw land that resembled what he had been told about Greenland and eventually he landed near the place where his father lived.

“Bjarni Herjólfsson was not credited for having found new land. Rather, he was mocked for not having gone ashore {in America],” says Englert.

Although he passed on his findings in Greenland, there was little interest in his reports until, after his father's death, he returned to Norway.

Here, Herjólfsson’s travel tales inspired Leif Ericsson to mount his own expedition to Greenland. He bought Herjólfssons ship and manned it with 35 crew members.

In the year 1002, Ericsson discovered North America. Here, he found grapes and berries, which is why he decided to call it Wineland. The rest we’ll have to leave for another time.
_________________________
References:

Sørensen, Irene Berg. 2012. “How Vikings navigated the world”. ScienceNordic. Posted: October 9, 2012. Available online: http://sciencenordic.com/how-vikings-navigated-world

The English inspired Vikings to build cities

The first cities and churches in medieval Denmark were probably inspired by the English, sources show. A historian sheds light on how the English influenced the Vikings, culturally as well as politically.

When Danish Vikings sailed across the North Sea and conquered England, they left their mark on the English language and place names. That’s common knowledge, at least to historians.

What’s perhaps less known is that the influence cut both ways. Although England was under Danish rule in the Viking Age, the English were culturally and politically more sophisticated than their neighbours to the east.

Historian Marie Bønløkke Spejlborg was one of the more than 300 Norse mythology researchers who attended the 15th International Saga Conference held recently in Aarhus, Denmark.

She is currently writing her PhD thesis about how the English some 1,000 years ago left a significant imprint on Danish society. It is, for instance, likely that it was the English who inspired Danes to organise themselves into cities, according to her historical sources.

“I’m trying to figure out how the Danes formed connections with the English during the Viking Age as they travelled back and forth,” she says.

From marketplaces to cities

“The English already had something that resembled a state with a functioning administration system. They had organised cities, whereas Denmark only had marketplaces.”

It’s therefore likely that the English inspired Danes to organise themselves into their first cities such as Viborg and Ringsted, she says.

“Back then the Vikings sailed back and forth between Denmark and England, and the Danes must have brought back some ideas from their travels,” says Spejlborg.

“There were for example a great number of people who, after having stayed in England perhaps for as long as ten years, returned to Denmark when Cnut the Great in 1018 disbanded his army. It would be strange if they didn’t bring something back home with them.”

She has spent the past 18 months trying to find out if it was the Danish Vikings who influenced the English or if the influence went both ways.

Shortage of clues

This has turned out to be a bit of an arduous task.

Thanks to archaeological finds, we know a great deal about what the Vikings left in England, and then there are place names such as the English town of Kirkby, whose name is rooted in Old Norse.

“But there hasn’t been much research into how the exchange between the two countries affected Denmark,” says the researcher. “This could perhaps be put down to the relative scarcity of written and archaeological sources.”

She has used written sources, chronicles and sagas to look for clues of an English influence on medieval Danish culture, society and religion.

This has been a lengthy process, since most of the relevant sources are written in either Old English or Latin.

“Then you need to sit down with a dictionary and take one sentence at a time. Fortunately, I’ve become quite good at skimming through the sources, so I can tell with relative ease what’s relevant and what’s not.”

English builders in Roskilde

Historians have long known that some of the oldest Danish churches were built in the English style. And some of the first Danish bishops were actually English, she explains.

"In the sources I can see that King Sweyn Forkbeard appointed bishops from England to Denmark. They must have had an influence on how the church was organised.”

The English were Christianised about 300 years before the Danes started to get rid of Norse mythology, and they had churches long before Harald Bluetooth was baptised around the year 960 and subsequently turned Denmark into a Christian country.

This is one of the factors, Spejlborg argues, that make it likely that the Danes drew inspiration from the English when they built their first churches. She mentions St Jørgensbjerg Church in the city of Roskilde (pictured above) as a clear example of the English influence.

“Some even believe it was constructed by English builders,” she adds.

The English also influenced Danish language

It wasn’t just the architecture and the organisation of churches that were inspired by the English. It’s also obvious that some Danish words have their origin in Old English, says the researcher.

The Danish word ‘kristendom’, for example, stems from the Old English ‘cristendom’.

The old Danish word ‘ærkibiskup’ (archbishop) comes from the Old Engish ‘arcebisceop’, and even though the word ‘kors’ (‘cross’) is derived from Latin, it’s likely that the word came to Denmark from England.
_________________________
References:

Ringgaard, Anne. 2012. “The English inspired Vikings to build cities”. Science Nordic. Posted: September 16, 2012. Available online: http://sciencenordic.com/english-inspired-vikings-build-cities

Skeletons Found at Mass Burial Site in Oxford Could Be 10th-Century Viking Raiders

Thirty-seven skeletons found in a mass burial site in the grounds of St John's College may not be who they initially seemed, according to Oxford researchers studying the remains.

When the bodies were discovered in the grounds of the college in 2008 by Thames Valley Archaeological Services, archaeologists speculated that they could have been part of the St Brice's Day Massacre in Oxford -- a well documented event in 1002, in which King Aethelred the Unredy ordered the killing of 'all Danes living in England'.

However, a new research paper, led by Oxford University, has thrown up a new theory -- that the skeletons may have been Viking raiders who were captured and then executed.

The skeletons were found in the ditch of a previously unknown Neolithic henge monument during excavations. They are mostly of men aged between 16 and 25 who were robust and taller than average. There is evidence that each individual was stabbed many times shortly before he died and severe wounds show they were brutally slaughtered. Some of the men also appear to have older scars, which could suggest that they were professional warriors. There is also evidence of charring on some of the skeletons, showing they may have been exposed to burning before burial.

Researchers from the Research Laboratory for Archaeology and the History of Art at the University of Oxford carried out a chemical analysis of collagen from the bones and the teeth of some of the individuals and concluded that they had had a substantial amount of seafood in their diet. It was higher in marine protein than that found in the local Oxfordshire population, as recorded in existing data.

Testing was done using strontium isotope analysis of tooth enamel, a technique which provides evidence of where an individual lived when the tooth formed. Strontium, a naturally occurring element in rocks and soils, is absorbed by plants and animals, and can be found in trace amounts in mammalian teeth. Strontium isotopes reflect the particular geological conditions so even small traces can be revealing of that individual's location.

They also looked at data relating to previous research in which an isotopic analysis of dismembered skeletons found in a burial pit at the Weymouth Ridgeway in Dorset identified the individuals as Scandinavian Viking raiders. The decapitated skeletons in Dorset, dated at between 890 and 1030 AD, and were thought to be a group of young men from different countries across Scandinavia. The isotopic analysis of the Dorset group and the individuals found in the mass burial site at St John's College show similarities.

Lead author Professor Mark Pollard, Director of the Research Laboratory in the School of Archaeology, said: 'Our latest research suggests that it is possible that the grisly remains at St John's College are the outcome of the documented massacre at St Frideswide's Church in AD 1002. Evidence of knife wounds and the burning of the bodies are consistent with the story of the burning of the church. However, following the chemical analysis of the teeth and bones, we are presented with an alternative interpretation: that they could have been a group of professional warriors, rather than a group of residents of Danish origin who were later rounded up and massacred.'
_____________ References:

Science Daily. 2012. "Skeletons Found at Mass Burial Site in Oxford Could Be 10th-Century Viking Raiders". Science Daily. Posted: May 1, 2012. Available online: http://www.sciencedaily.com/releases/2012/05/120501204839.htm

A. Pollard, P. Ditchfield, E. Piva, S. Wallis, C. Falys, S. Ford‘sprouting Like Cockle Amongst the Wheat’: The St Brice's Day Massacre and the Isotopic Analysis of Human Bones from St John's College, Oxford. Oxford Journal of Archaeology, 2012; 31 (1): 83 DOI: 10.1111/j.1468-0092.2011.00380.x

Oxford Viking massacre revealed by skeleton find

Evidence of a brutal massacre of Vikings in Oxford 1100 years ago has been uncovered by archaeologists.

At least 35 skeletons, all males aged 16 to 25 were discovered in 2008 at St John's College, Oxford.

Analysis of wound marks on the bones now suggests they had been subjected to violence.

Archaeologists analysing the find believe it dates from 1002 AD when King Ethelred the Unready ordered a massacre of all Danes (Vikings) in England.

The surprise discovery of the skeletons was made by Thames Valley Archaeological Services under the quadrangle at St John's College at the University of Oxford, before building work started on the site.

The bodies had not received any type of formal burial and they had been dumped in a mass grave on the site of a 4,000-year-old Neolithic henge monument.

Ceri Falys, an osteologist (a scientist who studies the structure of bones) from Thames Valley Archaeological Services, has been examining the bones since they were excavated. She has found a host of gruesome injuries on each of the individuals.

It was obvious at the time of excavation that many of the skulls had been fractured or crushed, but after piecing these skulls back together, she found that many of them were covered in blade and puncture wounds mostly to the back of the head.

One of the victims had puncture wounds to his pelvis that seem to have come from behind him and from the side, as well as substantial blade wounds to his skull, suggesting that he had been attacked from all sides by at least two different people.

These injuries were almost certainly fatal in each case, slicing through flesh and arteries right to the bone.

"Usually when people have been involved in hand to hand combat or are attacked you get evidence of this on the bones," Ceri Falys explained.

"You get cut marks on the forearms as they raise their arms to defend themselves, but we have minimal evidence of this on these skeletons, it seems that whoever was attacking them, it is likely that they were just trying to run away."'

It is possible that the Oxford skeletons were victims of an event called the St Brice's Day Massacre, recorded in a number of historical sources.

In AD1002, the Saxon king Ethelred the Unready recorded in a charter that he ordered "a most just extermination" of all the Danes in England.

He made the decision after he was told of a Danish plot to assassinate him.

The charter also recorded how on that day, the Danes in Oxford fled to St Fridewides church expecting to find refuge, but instead were pursued by the townspeople, who then set the church on fire.

Radiocarbon dating of the bones indicated that the bodies were dumped between AD960 and AD1020. This is compelling evidence for the association with St Brice's Day, explained archaeologist Sean Wallis, who directed the dig.

"We found evidence of charring on some of the bones, but not in the soil surrounding them.

"This ties in nicely with the documentary sources that the bodies may have been partially burnt prior to burial," he said.

Isotope analysis of the bones has shown that the men were eating a diet that was high in seafood.

This is an unusual find considering that they lived in inland Britain and perhaps a further indication that they may have been first or second generation Vikings.

A similar mass grave was found last year by Oxford Archaeology during work to build the Weymouth relief road.

It was radiocarbon dated to a similar period and again containing only young male victims, indicating that Anglo Saxon violence towards Vikings at the time may have been nationwide.

Ceri Falys will be talking to Dr Alice Roberts about the bones in a new series of BBC Two's Digging For Britain in September.
______________
References:

Ord, Louise. 2011. "Oxford Viking massacre revealed by skeleton find". BBC. Posted: August 12, 2011. Available online: http://www.bbc.co.uk/news/science-environment-14476039

Did Vikings navigate by polarized light?

Sunstone' crystals may have helped seafarers to find the Sun on cloudy days.

A Viking legend tells of a glowing 'sunstone' that, when held up to the sky, revealed the position of the Sun even on a cloudy day. It sounds like magic, but scientists measuring the properties of light in the sky say that polarizing crystals — which function in the same way as the mythical sunstone — could have helped ancient sailors to cross the northern Atlantic. A review of their evidence is published today in Philosophical Transactions of the Royal Society B¹.

The Vikings, seafarers from Scandinavia who travelled widely and settled in swathes of Northern Europe, the British Isles and the northern Atlantic from around 750 to 1050 AD, were skilled navigators, able to cross thousands of kilometres of open sea between Norway, Iceland and Greenland. Perpetual daylight during the summer sailing season in the far north would have prevented them from using the stars as a guide to their positions, and the magnetic compass had yet to be introduced in Europe — in any case, it would have been of limited use so close to the North Pole.

But Viking legends, including an Icelandic saga centring on the hero Sigurd, hint that these sailors had another navigational aid at their disposal: a sólarsteinn, or sunstone.

The saga describes how, during cloudy, snowy weather, King Olaf consulted Sigurd on the location of the Sun. To check Sigurd's answer, Olaf "grabbed a sunstone, looked at the sky and saw from where the light came, from which he guessed the position of the invisible Sun"². In 1967, Thorkild Ramskou, a Danish archaeologist, suggested that this stone could have been a polarizing crystal such as Icelandic spar, a transparent form of calcite, which is common in Scandinavia².

Light consists of electromagnetic waves that oscillate perpendicular to the direction of the light's travel. When the oscillations all point in the same direction, the light is polarized. A polarizing crystal such as calcite allows only light polarized in certain directions to pass through it, and can appear bright or dark depending on how it is oriented with respect to the light.

Centred on the light

Scattering by air molecules in the atmosphere causes sunlight to become polarized, with the line of polarization tangential to circles centred on the Sun. So Ramskou argued that by holding a crystal such as calcite up to the sky and rotating it to check the direction of polarization of the light passing through it, the Vikings could have deduced the position of the Sun, even when it was hidden behind clouds or fog, or was just beneath the horizon.

Historians have debated the possibility ever since, with some arguing that the technique would have been pointless, because it would only work if the crystal was pointed at patches of clear sky, and in such conditions it would be possible to estimate the position of the Sun with the naked eye, for example from the bright lining of cloud tops³.

Gábor Horváth, an optics researcher at Eötvös University in Budapest, and Susanne Åkesson, a migration ecologist from Lund University, Sweden, have been testing these assumptions since 2005. The special issue of Philosophical Transactions of the Royal Society B in which their review appears is dedicated to biological research on polarized light¹.

In one study, the researchers took photographs of partly cloudy or twilight skies in northern Finland through a 180° fisheye lens, and asked test subjects to estimate the position of the Sun⁴. Errors of up to 99° led the researchers to conclude that the Vikings could not have relied on naked-eye guesses of the Sun's position.

To check whether sunstones would work better, in 2005 they measured the polarization pattern of the entire sky under a range of weather conditions during a crossing of the Arctic Ocean on the Swedish icebreaker Oden^5,6.

Through the clouds

The researchers were surprised to find that in foggy or totally overcast conditions the pattern of light polarization was similar to that of clear skies. The polarization was not as strong, but Åkesson believes that it could still have provided Viking navigators with useful information.

"I tried such a crystal on a rainy overcast day in Sweden," she says. "The light pattern varied depending on the orientation of the stone."

She and Horváth are now planning further experiments to determine whether volunteers can accurately work out the Sun's position using crystals in various weather conditions.

Sean McGrail, who studied ancient seafaring at the University of Oxford, UK, before retiring, says that the studies are interesting but there is no real evidence to indicate that the Vikings actually used such crystals. "You can show how they could be used, but that isn't proof," he says. "People were navigating long before this without any instruments."

Surviving written records indicate that Viking and early medieval sailors crossed the north Atlantic using the Sun's position on clear days as a guide, in combination with the positions of coastlines, flight patterns of birds, migration paths of whales and distant clouds over islands, says Christian Keller, a specialist in North Atlantic archaeology at the University of Oslo. "You don't need to be a wizard," he says. "But you do need to combine a lot of different sorts of observations."

Keller says he is "totally open" to the idea that the Vikings also used sunstones, but is waiting for archaeological evidence. "If we find a shipwreck with a crystal on board, then I would be happy," he says.
________________
References:

Marchant, Jo. 2011. "Did Vikings navigate by polarized light?". Nature. Posted: January 31, 2011. Available online: http://www.nature.com/news/2011/110131/full/news.2011.58.html

Article References
1. Horváth, G. et al. Phil. Trans. R. Soc. B 366, 772-782 (2011).
2. Ramskou, T. Skalk 2, 16-17 (1967).
3. Roslund, C. & Beckman, C. Appl. Opt. 33, 4754-4755 (1994).
4. Barta, A. , Horváth, G. & Meyer-Rochow, V. B. J. Opt. Soc. Am. A 22, 1023-1034 (2005).
5. Hegedüs, R. , Åkesson, S. , Wehner, R. & Horváth, G. Proc. R. Soc. A 463, 1081-1095 (2007).
6. Hegedüs, R. , Åkesson, S. & Horváth, G. J. Opt. Soc. Am. A 24, 2347-2356 (2007).