Kamphuis, P.H. “D. Engelen, De Militaire Inlichtingendienst 1914-2000”. BMGN - Low Countries Historical Review 117, no. 1 (January 1, 2002): 131–133. Accessed May 18, 2024. https://bmgn-lchr.nl/article/view/URN%3ANBN%3ANL%3AUI%3A10-1-106480.