Twardowski, Łukasz. “The Role of the Vistula River As a Border on the Background of Historical Divisions of Poland and Its Importance in the Current Administrative Division”. Studies in Political and Historical Geography 4 (January 1, 2015): 221–252. Accessed December 8, 2025. https://www.czasopisma.uni.lodz.pl/studiageogr/article/view/18520.