SKIBA, A. N.; SHEMETKOV, L. A. Multiply $\mathfrak{L}$ formations of finite groupsformations of finite groups. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 52, n. 6, p. 783–787, 2000. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/4473. Acesso em: 5 dec. 2025.