Pypka, A.A., and D.Yu. Storozhenko. “On Some Types of Propermutable Subgroups and Their Generalizations in Finite Groups”. Reports of the National Academy of Sciences of Ukraine, no. 7 (July 28, 2017): 18–20. Accessed June 20, 2026. https://nasu-periodicals.org.ua/index.php/dp/article/view/7674.