Reinsma, R. β€œIn Memoriam Dr. J.J. Westendorp Boerma 1901-1970”. BMGN - Low Countries Historical Review 86, no. 1 (January 1, 1971): 157–157. Accessed February 2, 2023. https://bmgn-lchr.nl/article/view/URN%3ANBN%3ANL%3AUI%3A10-1-107774.