Hameed Hamz, Sattar, and Fatima Mizheir Majhool. “Strongly N-Proper Functions”. Journal of Al-Qadisiyah for Computer Science and Mathematics 3, no. 2 (October 1, 2017): 183–199. Accessed September 19, 2024. https://jqcsm.qu.edu.iq/index.php/journalcm/article/view/288.