3 IZA Discussion Papers
IZA Discussion Paper No. 7040
published in: American Economic Review, 2013, 103 (6), 2052-86
IZA Discussion Paper No. 5500
published in: E.A. Hanushek, S. Machin and S. Woessman (eds). Handbook of the Economics of Education, Amsterdam: Elsevier. 2011
IZA Discussion Paper No. 4001
published in: Journal of the European Economic Association, 2009, 7(2-3), 320 - 364