The Vikings have left many traces of their settlement which are still visible today. Archaeology provides physical evidence of their conquests, settlement and daily life. The study of place names and language shows the lasting effect which the Viking settlements had in the British Isles, and DNA analysis provides some insights into the effect the Vikings had on the genetic stock of the countries where they settled. All of this provides valuable information, but the only reason that we have an idea of the 'Vikings' as a people is their appearance in the written sources. Unfortunately, the value of the written evidence is limited. Not a lot of evidence survives, and much of what we have is either uninformative or unreliable. Many popular ideas about Vikings are nineteenth-century inventions. Others are the result of early historians accepting sources which modern scholars now regard as completely unreliable. In Scandinavia the Viking Age is regarded as part of prehistory because there are practically no contemporary written sources. Even in western Europe, the Viking Age is often seen as part of the 'Dark Ages', from which comparatively few historical records have survived. Surviving accounts of Viking activity were almost exclusively written by clergymen (神职人员). These monastic chronicles (编年史) outline broadly what happened, at what date. There are also sources of a more directly religious nature, such as the much-quoted letters of Alcuin, and Wulfstan's famous 'Sermon of the Wolf ', both of which chose to interpret the Viking raids as God's punishment on the Anglo-Saxons for their sins. Even the chronicles reflect the fact that the Vikings often attacked monasteries for their wealth, which created an obvious bias against them, and the hostile tone of these contemporary accounts has done much to create the popular image of Viking atrocities. However, modern historians have noted that the same sources show Christian rulers behaving equally unpleasantly, but without being condemned on religious grounds. We tend to think of the Vikings as a race of Scandinavian warriors, but the reality is more complex. Raids on the British Isles and the coasts of France and Spain were the work of Vikings from Norway and Denmark. The word Viking means one who lurks in a 'vik' or bay, in effect, a pirate. The word 'Viking' has come to describe a whole new age in Europe between about 800 and 1150. This is despite the fact that Vikings were not just pirates and warriors but also traders and colonists. But at the start of the Viking Age in the last decade of the 8th century, loot and adventure were the main goals of the Norwegians who raided in Scotland and Ireland and of the Danes who attacked England. Gold and silver treasures accumulated by the great monasteries could be converted into personal wealth and thus power, and captives could be sold as slaves. What better way for the young sons of good families to earn their way and see the world? The author's analysis of the Vikings mainly based on materials from ______ .