1. Department of Mathematics, College of Science and Arts, Jouf University, Al-Qurayat, Saudi Arabia
2. Department of Mathematics, Faculty of Science, Mansoura University, Mansoura, Egypt
3. Department of Basic Sciences, University of Engineering and Technology, Peshawar, Pakistan
4. Section of Mathematics, International Telematic University Uninettuno, Roma, Italy
5. Department of Statistics, College of Science, University of Jeddah, Jeddah, Saudi Arabia
6. Department of Mathematics, College of Science, King Saud University, Riyadh, Saudi Arabia