OLEJNIK, Karol. The Battle of Varna. Balcanica Posnaniensia. Acta et studia, [S. l.], v. 8, p. 5–16, 1997. DOI: 10.14746/bp.1997.8.1. Disponível em: https://pressto.amu.edu.pl/index.php/bp/article/view/54681. Acesso em: 8 aug. 2026.