Koval Т. V. Groups Proper Nonmaximal Subgroups of Which Are Cyclic or Minimal Noncyclic. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 52, n. 12, p. 1708–1710, 2000. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/4574. Acesso em: 6 dec. 2025.