Dovzhenko, S. A., and N. S. Chernikov. “Primary Graded Groups With Complementable Non-Frattini Subgroups”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 51, no. 10, Oct. 1999, pp. 1324–1333, https://umj.imath.kiev.ua/index.php/umj/article/view/4731.