Kieavan Letter
The Kievian Letter is an early 10th-century (ca. 930) letter long thought to be written by aKhazarian Jewish community in Kiev. The letter, aHebrew-language recommendation written on behalf of one member of their community, was part of an enormous collection brought to Cambridge by Solomon Schechter from the Cairo Geniza. It was discovered in 1962 during a survey of the Geniza documents by Norman Golb of theUniversity of Chicago. (quote - https://en.wikipedia.org/wiki/Kievian_Letter )
References:
University of Cambridge - Digital Library
http://cudl.lib.cam.ac.uk/view/MS-TS-00012-00122/1
Instute of History - Ukraine (National Academy of Sciences Ukraine)
http://history.org.ua/JournALL/ruthenica/ruthenica_2011_10/2.pdf
Liveleak
http://www.liveleak.com/view?i=eb0_1183163642
Этническая история Северной Еврази
From the Kievan Rus Database
http://kievan-rus2.appspot.com/Kievan_Letter.html