KHMELNITSKII, N. A.; CHERNIKOV, N. S. Locally Nilpotent Groups with Weak Conditions of π-Layer Minimality and π-Layer Maximality. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 54, n. 7, p. 991–997, 2002. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/4135. Acesso em: 7 apr. 2025.