3 IZA Discussion Papers
IZA Discussion Paper No. 5986
published in: Research Policy, 2012, 41 (5), 913–927
IZA Discussion Paper No. 3084
revised version is published in: Baltic Journal of Economics, 2009, 9 (1), 5-29
IZA Discussion Paper No. 273
published in: Economic Journal, 2006, 116 (511), 382-407