Trebenko, D. Y., and N. S. Chernikov. “Quotient Groups of Locally Graded Groups and Groups of Certain Kurosh-Chernikov Classes”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 50, no. 11, Nov. 1998, pp. 1545–1553, https://umj.imath.kiev.ua/index.php/umj/article/view/4807.