SKIBA, A. N.; ZHANG, Chi. On $\Sigma_t^{σ}$ -closed classes of finite groups. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 70, n. 12, p. 1707–1716, 2018. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/1669. Acesso em: 27 apr. 2025.