Algadid, Yousef, and Waleed Hannun. “On Some Finitely Generated Subsemigroups of S(X)”. Journal of Humanitarian and Applied Sciences 5, no. 9 (June 30, 2020): 135–138. Accessed November 21, 2024. https://khsj.elmergib.edu.ly/index.php/jhas/article/view/355.