Russka︠i︡a i arm︠i︡anska︠i︡a srednevekovye literatury - Aĭvaz︠i︡an, K. V. (Kazar Vartanovich), 1913-; Likhachev, Dmitriĭ Sergeevich ("Nauka," Leningradskoe otd-nie, 1982)