Li, X. H., and Y. Xu. “$s$-Conditionally Permutable Subgroups and $p$-Nilpotency of Finite Groups”. Ukrains’kyi Matematychnyi Zhurnal, vol. 66, no. 6, June 2014, pp. 858–864, https://umj.imath.kiev.ua/index.php/umj/article/view/2184.