4 IZA Discussion Papers
IZA Discussion Paper No. 7603
IZA Discussion Paper No. 4177
published in: Empirical Economics, 2009, 37 (3), 627 - 652
IZA Discussion Paper No. 713
IZA Discussion Paper No. 580
published in: Schmollers Jahrbuch: Zeitschrift für Wirtschafts- und Sozialwissenschaften /Journal of Applied Social Science Studies, 2003, 123(1), 3-14