GudivokP. M., and ShapochkaI. V. “On Chernikov<em class="a-Plus-plus">p</Em&gt;-Groups”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 51, no. 3, Mar. 1999, pp. 291–304, https://umj.imath.kiev.ua/index.php/umj/article/view/4613.