1. Willem Bonger, Introduction to Criminology, London: Methuen and Company, 1936, p. 82.
2. W. A. Bonger, Criminality and Economic Conditions, Boston, MA: Little, Brown and Company, 1916.
3. For more detail see Jakob M. Van Bemmelen, ‘Pioneers in Criminology: VIII Willem Bonger’, The Journal of Criminal Law, Criminology, and Police Science, Vol. 46, 1955, pp. 293–302.
4. W. Bonger, Race and Crime, (1943), [1939], New York: Columbia University Press, 1943.
5. See John H. Wigmore, ‘Willem Bonger’, Journal of Criminal Law and Criminology, Vol. 31, Part 5, 1941, p. 657.