Liman, F. N., and T. D. Lukashova. “On the Norm of Decomposable Subgroups in Nonperiodic Groups”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 67, no. 12, Dec. 2015, pp. 1679-8, http://umj.imath.kiev.ua/index.php/umj/article/view/2100.