2 IZA Discussion Papers
IZA Discussion Paper No. 6098
published in: PLoS ONE, 9(11): e111903. doi: 10.1371/journal.pone.0111903, http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0111903
IZA Discussion Paper No. 5626
published in: Economic and Social Review, 2011, 42(3), 237–270