Li, X. H., and Y. Xu. 2014. “Second Maximal Subgroups of a Sylow P-Subgroup and the P-Nilpotency of Finite Groups”. Ukrains’kyi Matematychnyi Zhurnal 66 (5): 694–698. https://umj.imath.kiev.ua/index.php/umj/article/view/2170.