CZEPIL, B.; TURNER, F. J. The Significance of the Frontier in American History. Border and Regional Studies, [S. l.], v. 2, n. 2, p. 139–162, 2014. DOI: 10.25167/ppbs524. Disponível em: https://czasopisma.uni.opole.pl/index.php/p/article/view/524. Acesso em: 22 nov. 2024.