Menkens’ analysis of Lübbe's archaeological World Atlas (1976, page 184)
‘The Fatjanovo Group developed in the forest zone of central Russia and eastern Europe. It is mainly known for its shallow burial grounds. The Fatjanovo culture on the upper Volga and the related Balanovo Group of the middle Volga region belong to the large corded ware/battle axe complex of northern Europe, whose graves are filled with battle axes as one of the most characteristic burial goods of the dead ... North of the territories inhabited by of the Fatjanovo culture, the Oststeek culture extended westwards to Poland and evolved here without major interruption from the 3rd millennium B.C. (with a corded ware phase that corresponded with other groups using the same technique) until the 8th century B.C. The area was known for vigorous trade with the Aunjetitz culture of central Europe during the first half of the 2nd millennium B.C.’
We can therefore assume that this Baltic culture, which developed undisturbed and without interruption from the 3rd millennium B.C. to the 8th century B.C., was actually the Fryas living along the Baltic Sea. The World Atlas reports on the pre-Roman Iron Age (page 180):
‘The lowlands of north-central Europe and southern Scandinavia lay outside the area inhabited by the Celtic Hallstatt and Latène cultures. Here, the local Bronze Age cultures simply lived on, except that its representatives acquired the ability to process iron in the 2nd half of the 1st millennium B.C. These northern cultures are mainly known for their cemeteries with usually shallow graves, which are sometimes interspersed with burial mounds. There is no shortage of burial gifts. And they include a fair amount of imported items from the Celtic world. Settlements are very common as well. Perhaps the best known is the village of rectangular houses close to Biskupin (near Znin in north-west Poland). At the time, the oldest terps (settlements on flat, mounded hills to protect against flooding) were built in the Netherlands – near Ezinge, for example.