3 IZA Discussion Papers
IZA Discussion Paper No. 8177
published in: Labour Economics, 2015, 34, 51-63
IZA Discussion Paper No. 7767
revised version published in: Industrial Relations Journal, 2014, 45 (6), 543 - 561
IZA Discussion Paper No. 7668
published in: European Educational Research Journal, 2014, 13(3), 282-294