DROZDEK, A. Duty during the reign of the Piast. Miscellanea Historico-Iuridica, [S. l.], v. 15, n. 1, p. 33–47, 2017. Disponível em: http://miscellanea.uwb.edu.pl/article/view/115. Acesso em: 1 oct. 2022.