Bilczak, Wasyl, and Michał Bilczak. “Social Security of Population As a Basis for Stable Growth of Border Regions”. Olsztyn Economic Journal 11, no. 4 (December 30, 2016): 331–342. Accessed May 23, 2022. https://czasopisma.uwm.edu.pl/index.php/oej/article/view/2936.