1. Department of Mathematics, Faculty of Science, Sohag University, Sohag, Egypt
2. Department of Mathematics, Faculty of Science, Islamic University of Madinah, Madinah, Saudi Arabia
3. Mathematics Department, College of Science, King Khalid University, Abha, Saudi Arabia
4. Section of Mathematics, International Telematic University Uninettuno, Roma, Italy
5. Department of Basic Sciences, University of Engineering and Technology, Peshawar, Pakistan