83 IZA Discussion Papers
IZA Discussion Paper No. 355
revised version published in: Labour Economics, 2008, 15 (6), 1270-1295
IZA Discussion Paper No. 149
published in: Economic Journal, 2008, 118 (525), 235–257
IZA Discussion Paper No. 121
published in: Michael Lechner and Friedhelm Pfeiffer (eds.), Econometric Evaluation of Labour Market Policies, Physica-Verlag (2001), 125-152