4 IZA Discussion Papers
IZA Discussion Paper No. 6715
IZA Discussion Paper No. 6566
IZA Discussion Paper No. 5830
published in: Social Science and Medicine, 2011, 73 (4), 535 - 539
IZA Discussion Paper No. 3583
published in: Journal of Economic Behavior and Organization, 2011, 77(3), 265-284