Selmi, R., Department of Mathematics, College of Science, Northern Border University, P.O. Box 1321, Arar, 73222, KSA; University of Gabes, Faculty of Science of Gabes, Department of Mathematics, Gabes 6072, Tunisia; University of Tunis El Manar, Faculty of Science of Tunis, Laboratory of Partial Differential Equations and Applications (LR03ES04), Tunis, 1068, Tunisia, Tunisia