Chernikov, S. N. “Infinite Non-Abelian Groups Where All the Infinite Non-Abelian Subgroups Are Invariant”. Ukrains’kyi Matematychnyi Zhurnal 23, no. 5 (September 3, 1971): 604–628. Accessed December 6, 2025. https://umj.imath.kiev.ua/index.php/umj/article/view/8333.