3 IZA Discussion Papers
IZA Discussion Paper No. 3640
published in: Journal of Economic Literature, 2009, 47(1), 1-81
IZA Discussion Paper No. 1873
revised version published in: Economics Letters , 2008, 98 (3), 309-319
IZA Discussion Paper No. 91
published in: M. Lechner, F. Pfeiffer (eds.), Econometric Evaluation of Labour Market Policies, Heidelberg: Physica, 2001, 43-58