I. Cornelissen, Alleen tegen de wereld. Joop Zwart, de geheimzinnigste man van Nederland. BMGN - Low Countries Historical Review, [S. l.], v. 119, n. 1, p. 131–132, 2004. DOI: 10.18352/bmgn-lchr.6006. Disponível em: https://ojstest.minions.amsterdam/article/view/URN%3ANBN%3ANL%3AUI%3A10-1-106886.. Acesso em: 16 sep. 2024.