Hijazi, R. A. (2011). Mutually Permutable Products of Finite Groups. ISRN Algebra, (), 106-109. https://www.airitilibrary.com/Article/Detail?DocID=20906285-201112-201202230022-201202230022-110-113
KLEIN, A. A., & BELL, H. E. (2003). ON SOME CENTER-LIKE SUBSETS OF GROUPS. International Journal of Mathematics and Mathematical Sciences, 2003(), 2583-2586-197. https://doi.org/10.1155/S016117120330328X