@techreport{Willekens2007,
author = {Willekens, F.J.},
title= {Multistate model for biographic analysis and projection. Working Paper 2007/1},
year = {2007},
URL = {http://www.nidi.nl/shared/content/output/papers/nidi-wp-2007-01.pdf
%[21 March 2014},
publisher = {NIDI},
address = {The Hague},
}