VASIL'EV, V. A.; SKIBA, A. N. On one generalization of modular subgroups. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 63, n. 10, p. 1314–1325, 2011. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/2808. Acesso em: 5 dec. 2025.