aaron ii abkhaz people alexander vasiliev alp iluetuer alp tarkhan atil azov balanjar baranjars barjik barsils black sea burtas busir byzantine empire caucasus mountains cecil roth chersonesos circassians crimea crimean goths david of taman east slavs feodosiya george vernadsky georgius tzul hazer tarkhan international standard book number john of gothia kabar kazarki kerch khamlij khazar correspondence khazar language khazaran khazars khazars in fiction khumar kiev kievian letter kipchaks kuzari lebedias leo iv the khazar lezgins list of khazar rulers mandgelis document meshchera mikhail artamonov mordvins mountain jews north caucasian huns oghuz turks oleg of novgorod onogurs papatzys parsbit pax khazarica pechenegs portage radhanite ras tarkhan red jews rostov oblast russia sabir people saltovo-mayaki sambalut samiran samosdelka saqsin sarir schechter letter semikarakorsk sfengus sudak sviatoslav i of kiev taman peninsula theodora of khazaria theophilus tmutarakan trade route from the varangians to the greeks tsimlyansk reservoir tzitzak volga trade route yitzhak ha-sangari