1. Department of Mathematics, AL-Qunfudhah University College, Umm Al-Qura University, KSA
2. Department of Mathematics, Faculty of Sciences of Tunis, University of Tunis El-Manar, 1060 Tunis, Tunisia
3. Gafsa University, Gafsa, Tunisia
4. High School of Sciences and Technology of Hammam Sousse, University of Sousse, Tunisia