ChernikovN. S. “On Periodic Locally Solvable Groups Decomposable into the Product of Two Locally Nilpotent Subgroups”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 52, no. 7, July 2000, pp. 965-70, https://umj.imath.kiev.ua/index.php/umj/article/view/4495.