BROUWER, J. P. van der Steen, Cals, koopman in verwachtingen 1914-1971. BMGN - Low Countries Historical Review, [S. l.], v. 121, n. 2, p. 366–368, 2006. DOI: 10.18352/bmgn-lchr.6439. Disponível em: https://bmgn-lchr.nl/article/view/URN%3ANBN%3ANL%3AUI%3A10-1-107939. Acesso em: 4 may. 2024.