984 IZA Discussion Papers
IZA Discussion Paper No. 69
revised version published in: Journal of Economic and Social Measurement, 2007, 32 (1), 15-22
IZA Discussion Paper No. 60
IZA Discussion Paper No. 57
published in: Journal of Human Resources, 2000, 35 (3), 550-569;
see IZA Reprints 54/00
see IZA Reprints 54/00
IZA Discussion Paper No. 51
published in: Industrial and Labor Relations Review, 2001, 54 (3), 647-662