L.H. Maas, Pro patria. Werken, leven en streven van Gerrit Kalff 1856-1923. BMGN - Low Countries Historical Review, [S. l.], v. 115, n. 1, p. 148–150, 2000. DOI: 10.18352/bmgn-lchr.5187. Disponível em: https://ojstest.minions.amsterdam/article/view/URN%3ANBN%3ANL%3AUI%3A10-1-105951.. Acesso em: 30 jun. 2024.