Shemetkov, L. A. “Complements and Supplements to Normal Subgroups of Finite Groups”. Ukrains’kyi Matematychnyi Zhurnal 23, no. 5 (September 3, 1971): 678–689. Accessed December 5, 2025. https://umj.imath.kiev.ua/index.php/umj/article/view/8340.