Brands, M.C. “In Memoriam Dr. J. Haak 1924-1970”. BMGN - Low Countries Historical Review 85, no. 3 (January 1, 1970): 359–360. Accessed May 9, 2024. https://bmgn-lchr.nl/article/view/URN%3ANBN%3ANL%3AUI%3A10-1-107831.