KIJAS, Artur. Small nomadic peoples, Berendei tribe, Chornye Klobuki (Black Hats) and Bierladnicy Tribe vs. Kievan Rus (Ruthenia). Balcanica Posnaniensia. Acta et studia, [S. l.], v. 14, p. 145–156, 2007. DOI: 10.14746/bp.2007.14.11. Disponível em: https://pressto.amu.edu.pl/index.php/bp/article/view/52834. Acesso em: 4 oct. 2026.