Li, X. H., and Y. Xu. “Second Maximal Subgroups of a Sylow <em class="a-Plus-plus">p</em>-Subgroup and the <em class="a-Plus-plus">p</Em&gt;-Nilpotency of Finite Groups”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 66, no. 5, May 2014, pp. 694–698, https://umj.imath.kiev.ua/index.php/umj/article/view/2170.