Nowak, A., A. Krukowski, and E. Wójcik. “THE CHANGES IN PRODUCTIVITY OF PRODUCTION FACTORS IN COMMERCIAL FARMS IN POLAND IN 2004 AND 2012”. Acta Scientiarum Polonorum. Oeconomia, vol. 14, no. 3, Sept. 2015, pp. 105-1, https://aspe.sggw.edu.pl/article/view/434.