S. N. Chernikov and N. S. . Chernikov, “Complementability criterion of periodical almost soluble subgroups in the group containing it”, Ukr. Mat. Zhurn., vol. 44, no. 6, pp. 822–826, Jul. 1992, Accessed: Dec. 06, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/8016