Borecka, Anna, and Elżbieta Sowula-Skrzyńska. 2009. “Improving the Economic Situation of Pig Livestock Farms by Taking Advantage of the Opportunities Offered by Producer Group Membership”. The Scientific Journal European Policies, Finance and Marketing, no. 2(51) (December):297-306. https://pefim.sggw.edu.pl/article/view/1592.