3 IZA Discussion Papers
IZA Discussion Paper No. 10376
IZA Discussion Paper No. 6234
published in: American Journal of Agricultural Economics, 2011, 93 (2), 505–511
IZA Discussion Paper No. 1965
published in: American Journal of Agricultural Economics, 2007, 89 (4), 852-863; excerpts also publishd in Economics Letters, 2008, 98 (1), 31-34