Rovers, Frits. “C. Kirkels, Architect Van Onderwijsvernieuwing. Denken En Daden Van Gerrit Bolkestein 1871-1956”. BMGN - Low Countries Historical Review 125, no. 4 (January 1, 2010). Accessed April 26, 2024. https://bmgn-lchr.nl/article/view/URN%3ANBN%3ANL%3AUI%3A10-1-108226.