POLOVITSKY , Ya. D. Groups with a condition of layered minimality . Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 44, n. 6, p. 847–851, 1992. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/8022. Acesso em: 6 dec. 2025.