Potapova , O. B., and N. S. Samoilenko. “Experience of the Countries of Southeast Europe in Cross-Border Cooperation (end of XX – Beginning of XXI century). ”. Zaporizhzhia Historical Review, Vol. 2, no. 45, Dec. 2020, pp. 224-8, https://istznu.org/index.php/journal/article/view/856.