1. Department of Mathematics, College of Science, Qassim University, Post Box 6644, Buraidah 51452, Qassim, Kingdom of Saudi Arabia
2. Preparatory Institute for Scientific and Technical Studies of Marsa, Carthage University, Sidi Bou Said Road, Post Box 51. 2075, La Marsa, Tunis, Tunisia
3. Department of Mathematics, Faculty of Sciences, University of Gabès, Tunisia