L.J. Giebels, Beel, van vazal tot onderkoning. Biografie 1902-1977. BMGN - Low Countries Historical Review, [S. l.], v. 113, n. 1, p. 138–139, 1998. DOI: 10.18352/bmgn-lchr.4665. Disponível em: https://ojstest.minions.amsterdam/article/view/URN%3ANBN%3ANL%3AUI%3A10-1-105361.. Acesso em: 2 jul. 2024.