Kurdyś-Kujawska, A., and A. Oleńczuk-Paszel. “Changes of Levels of Rent and Risk in the Activity of Rural Farms in Poland”. Journal of Agribusiness and Rural Development, Vol. 28, no. 2, Dec. 2013, pp. 151-9, http://www1.up.poznan.pl/jard/index.php/jard/article/view/627.