LESZKA, Mirosław J. Bulgaria and the Khazars towards fights for power in Byzantium at the beginings of the eight century. Balcanica Posnaniensia. Acta et studia, [S. l.], n. 9/10, p. 49–62, 1999. DOI: 10.14746/bp.1999.9-10.5. Disponível em: https://pressto.amu.edu.pl/index.php/bp/article/view/54620. Acesso em: 14 aug. 2026.