WASILEWSKI, Tadeusz. Boris I – prince or king of Bulgaria?. Balcanica Posnaniensia. Acta et studia, [S. l.], v. 2, p. 33–42, 1985. DOI: 10.14746/bp.1985.2.3. Disponível em: https://pressto.amu.edu.pl/index.php/bp/article/view/54814. Acesso em: 2 oct. 2026.