FOLFAS, Paweł. Regions in the United States and the European Union - GDP per Capita, Convergence Processes and Spatial Dependencies. Studia Oeconomica Posnaniensia, Poznan, Polska, v. 5, n. 1, p. 75–85, 2017. DOI: 10.18559/SOEP.2017.1.5. Disponível em: https://journals.ue.poznan.pl/soep/article/view/3495. Acesso em: 3 sep. 2026.