The Making of Central and Eastern Europe by
Francis Dvornik
The Polish Research Centre Ltd, London
1949

Pages 61-62 in Chapter II THE EMPEROR OTTO I, POLAND, BOHEMIA AND RUSSIA
. . .     As early as the eighth century, explorations on the Baltic brought them [Norsemen] to the Balt and Finnish populations on its eastern shores, where they must have heard of the two flourishing empires established on the Volga by the Khazars and the Bulgars. The Khazars at that time carried on a brisk trade with the Arabs of Bagdad, a city that was then at the height of its prosperity and highly appreciated the products from the north, especially furs which were plentiful and slaves. The Arabs paid well for these commodities and the Khazars rose to be the most influential intermediaries between the interior of future Russia, the Slavonic tribes living there and the Arabs. The Volga was a unique artery of communication.     The Jewish elements always numerous on the shores of the Black Sea and the Sea of Azov must have played an important part of those commercial exchanges, since we know that their activities in Khazaria were brisk enough to convert the Khagan of the Khazars and a great portion of native population to their own faith.
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Footnote 51: I have treated the history of the Khazars and their conversion to Judaism in detail in my book Les Légendes de Constantin et de Méthode vues des Byzance, (1933) . . . An abundant bibliography on the subject will be found there.