425 IZA Discussion Papers
IZA Discussion Paper No. 272
IZA Discussion Paper No. 209
IZA Discussion Paper No. 43
IZA Discussion Paper No. 33
published in: American Economic Review, 1999, 89 (2), 81-88
IZA Discussion Paper No. 11
published in: Applied Economics, 2002, 34 (7), 865-876