Some of this history is still controversial (namely, the actual location of Sarkel). Here is what I extracted from the book
S. Pletneva, "Essays on Khazar archeology," ("Очерки хазарской археологии") Jerusalem, 1999,
written mostly on the basis of archeological excavations, namely, Artamonov's expedition (Artamonov was Pletneva's PhD advisor).
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