Łuczka-Bakuła, W., and L. Łuczka-Bakuła. “Oaps’ Activity in the Labour Market in the Context Of Survey Research”. Journal of Agribusiness and Rural Development, Vol. 30, no. 4, Dec. 2013, pp. 177-86, http://www1.up.poznan.pl/jard/index.php/jard/article/view/693.