OZOLAS, Romualdas. New Theses. Problemos, [S. l.], v. 3, p. 98–100, 1969. DOI: 10.15388/Problemos.1969.3.5750. Disponível em: https://www.journals.vu.lt/problemos/article/view/5750.. Acesso em: 6 may. 2024.