JORDANOV, Ivan. The Mediaeval Bulgarian state according to evidence from numismatics and sphragystics. Balcanica Posnaniensia. Acta et studia, [S. l.], v. 2, p. 19–32, 1985. DOI: 10.14746/bp.1985.2.2. Disponível em: https://pressto.amu.edu.pl/index.php/bp/article/view/54813. Acesso em: 4 oct. 2026.