3 IZA Discussion Papers
IZA Discussion Paper No. 8662
published in: Research Policy, 2015, 44 (9), 1714 - 1733
IZA Discussion Paper No. 1799
published in: Review of Economic and Statistics, 2006, 88(3), 472-481
IZA Discussion Paper No. 1372
published in: Economic and Social Review, 2004, 35(3), 267-288