3 IZA Discussion Papers
IZA Discussion Paper No. 5325
improved version is available here
IZA Discussion Paper No. 2124
published as "When is it foolish to reward for A while benefiting from B" in: Journal of Labor Economics, 2008, 26 (4), 595-619
IZA Discussion Paper No. 765
improved version available as IZA Discussion Paper No. 2124