ChernikovS. N. “Infinite Non-Abelian Groups Where All the Infinite Non-Abelian Subgroups Are Invariant”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 23, no. 5, Sept. 1971, pp. 604-28, https://umj.imath.kiev.ua/index.php/umj/article/view/8333.