Great Soviet Encyclopedia, 3rd edition, 1973
"In the first century A.D. the region now occupied by Nagorno-Karabakh Autonomous Oblast was part of the province of Artsakh, which belonged to Caucasian Albania. Feudal relations developed in the third through fifth centuries, and Christianity began to spread. In the early eighth century the Arabs conquered Artsakh, as well as all of Albania, and Islam penetrated the area. (Until that time Gregorianism had flourished among the Christian population.) Artsakh was part of the Albanian kindgdom in the ninth and tenth centuries. In the mid-11th century it was invaded by the Seljuk Turks... In the 1230's, Artsakh was conquered by the Mongols, and from that time most of its territory was called Karabakh."
(Great Soviet Encyclopedia, 3rd edition, 1973, "NKAO, Historial Survey")