2 IZA Discussion Papers
IZA Discussion Paper No. 4451
revised version published as 'Comparing Treatments across Labor Markets: An Assessment of Nonexperimental Multiple-Treatment Strategies' in: Review of Economics and Statistics, 2013, 95(5), 1691-1707
IZA Discussion Paper No. 716
published in: Journal of Applied Econometrics, 2009, 24 (2), 338-365.