RUSIELIK, Robert, and Wojciech ZBARASZEWSKI. “The Efficiency of Scientific and Tourism Activity of Polish National Parks With Use DEA Method”. Economic and Environmental Studies 14, no. 3 (31) (December 1, 2020): 283–297. Accessed November 23, 2024. https://czasopisma.uni.opole.pl/index.php/ees/article/view/2883.