KAMENSKIKH, M.S. Soviet-bulgarian interaction in Perm region in the 1950s. Perm Federal Research Centre Journal, [S. l.], n. 3, p. 80–84, 2020. DOI: 10.7242/2658-705X/2020.3.7. Disponível em: https://journal.permsc.ru/index.php/pscj/article/view/PSCJ2020n3p7. Acesso em: 14 apr. 2026.