6 IZA Discussion Papers
IZA Discussion Paper No. 16284
IZA Discussion Paper No. 9981
IZA Discussion Paper No. 8214
IZA Discussion Paper No. 5985
IZA Discussion Paper No. 3784
revised version published in: Journal of Labor Economics, 2011, 29 (3), 513-547
IZA Discussion Paper No. 1143
published in: Economic Journal, 2009, 119 (539), 1208 - 1224