4 IZA Discussion Papers
IZA Discussion Paper No. 6050
IZA Discussion Paper No. 2400
IZA Discussion Paper No. 1002
published in: American Economic Review, 2007, 97 (1), 298-317
IZA Discussion Paper No. 927
published in: Journal of the European Economic Association, 2004, 2 (2-3), 216-228