V. A. Kovaleva, “Finite groups with given systems of $K-\mathfrak{U}$-subnormal subgroups”, Ukr. Mat. Zhurn., vol. 68, no. 1, pp. 52–63, Jan. 2016, Accessed: Dec. 05, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/1821