3 IZA Discussion Papers
IZA Discussion Paper No. 8921
published in: IZA Journal of European Labor Studies 2015, 4:11
IZA Discussion Paper No. 3502
published in: Journal of Common Market Studies, 2010, 48 (3), 661-685
IZA Discussion Paper No. 3161
substantially revised and rewritten version available as IZA DP No. 3502