2 IZA Discussion Papers
IZA Discussion Paper No. 6213
published in: Journal of Economic Literature, 2012, 50 (1), 96 - 102
IZA Discussion Paper No. 354
revised version published as 'On the Role of Counterfactuals in Inferring Causal Effects' in: Foundations of Science, 2004, 9 (1), 65-101