Amiri, S.M. Jafarian, and Hojjat Rostami. “The Probability That an Ordered Pair of Elements Is an Engel Pair”. Journal of the Indonesian Mathematical Society 25, no. 2 (July 10, 2019): 121–127. Accessed May 3, 2024. https://jims-a.org/index.php/jimsa/article/view/693.