SOLOVJOVAS, Nikolajus. Neighbourhood Relations. Problemos, [S. l.], v. 15, p. 98–103, 1975. DOI: 10.15388/Problemos.1975.15.5578. Disponível em: https://www.journals.vu.lt/problemos/article/view/5578.. Acesso em: 16 aug. 2024.