O. Vries, Het Heilige Roomse Rijk en de Friese vrijheid. BMGN - Low Countries Historical Review, [S. l.], v. 103, n. 3, p. 440–442, 1988. DOI: 10.18352/bmgn-lchr.2992. Disponível em: https://ojstest.minions.amsterdam/article/view/URN%3ANBN%3ANL%3AUI%3A10-1-103368.. Acesso em: 22 nov. 2024.