SMIRNOVAS, Anatolijus. People and Social Progress. Problemos, [S. l.], v. 5, p. 23–28, 1970. DOI: 10.15388/Problemos.1970.5.5775. Disponível em: https://test.zurnalai.vu.lt/problemos/article/view/5775. Acesso em: 27 oct. 2025.