923 IZA Discussion Papers
IZA Discussion Paper No. 198
published in: European Early Childhood Education Research Journal, 2003, 11 (2), 159-175
IZA Discussion Paper No. 158
published in: Journal of Population Economics, 15 (4), 2002, 757-772
IZA Discussion Paper No. 157
published in: Labour Economics, 2001, 8 (6), 621-648