1. Faculty of sciences and humanities of Hawtat Sudair, Department of Mathematics, University of Majmaah , Majmaah, Saudi Arabia.
2. Faculty of Sciences of Bizerte, Department of Mathematics, University of Carthage , Jarzouna, Tunisia.
3. Department of Mathematics, Colleges of technology of Jeddah , Jeddah, Saudi Arabia.
4. Faculty of Sciences of Tunis, Department of Mathematics, University of Manar , Tunis, Tunisia.