↑ ""A violent civil war took place during the 820s [...] The losers of the internal political struggle, known as Kabars, fled northward to the Varangian Rus' in the upper Volga region, near Rostov, and southward to the Magyars, who formerly had been loyal vassals of the Khazars. The presence of Kabar political refugees from Khazaria among the Varangian traders in Rostov helped to raise the latter's prestige, with the consequence that by the 830s a new power center known as the Rus' Kaganate had come into existence."Magocsi, Paul Robert (2010). A History of Ukraine: A Land and Its Peoples. Toronto: University of Toronto Press. tr. 62.
↑ "By the end of the 9th century, Helgi/Oleh the empire builder [...] had from his capital in Kiev gained control over most of the East Slavic tribes [to] the upper Volga in the far north."Magocsi, Paul Robert (2010). A History of Ukraine: A Land and Its Peoples. Toronto: University of Toronto Press. tr. 66.
↑ E.g., Christian, David. A History of Russia, Mongolia and Central Asia. Blackwell, 1999. p. 38.
