Czyżewski, B., and A. Brelik. “CONSIDERATIONS ON A LAND INTRINSIC PRODUCTIVITY AND ITS DETERMINANTS IN A SUSTAINABLE AGRICULTURE”. Acta Scientiarum Polonorum. Oeconomia, Vol. 14, no. 3, Sept. 2015, pp. 39-48, https://js.wne.sggw.pl/index.php/aspe/article/view/4180.