Siudek, T., and A. Zawojska. “COMPETITIVENESS IN THE ECONOMIC CONCEPTS, THEORIES AND EMPIRICAL RESEARCH”. Acta Scientiarum Polonorum. Oeconomia, Vol. 13, no. 1, Mar. 2014, pp. 91-108, https://js.wne.sggw.pl/index.php/aspe/article/view/4110.