PANIC, Idzi. Duces opolienses domini in Ratibor. Revisiting the issue of the titles of duke Przemysław from Racibórz and time of formation of Racibórz and Cieszyn Duchys. Wieki Stare i Nowe, [S. l.], v. 5, p. 82–94, 2007. DOI: 10.31261/WSN.2007.07.05. Disponível em: https://journals.us.edu.pl/index.php/WSN/article/view/18693. Acesso em: 15 nov. 2026.