4 IZA Discussion Papers
IZA Discussion Paper No. 11530
IZA Discussion Paper No. 7743
published in: Economics Letters, 2015, 127(0), 76-80
IZA Discussion Paper No. 1822
revised version published in: Journal of Economic and Social Measurement, 2008, 33 (1), 27-38
IZA Discussion Paper No. 836
published in: Economic Inquiry, 2005, 43 (4), 766-772