Feskens, Remco, Joop Hox, Hans Schmeets, and Willem Wetzels. “Incentives and Ethnic Minorities: Results of a Controlled Randomized Experiment in the Netherlands”. Survey Research Methods 2, no. 3 (December 19, 2008): 159-165. Accessed September 15, 2019. https://ojs.ub.uni-konstanz.de/srm/article/view/71.