Summary - PDF - http://www.wodc.nl/eng/Images/1338_summary_tcm12-126839.pdf
Sikkel, D., Heijden, P.G.M. van der, Gils, G. van
"This report gives an overview of methods that can in general be used to make inferences about the size of hidden populations. More in particular the suitability of the methods is discussed to determine the size of populations of illegal foreigners and the sizes of subpopulations of these groups, for instance by nationality or by place of residence."
