1. Department of Mathematics, Faculty of Science, Education and Arts, Sana’a University, Sana’a, Yemen
2. Mathematics Department, College of Science, King Khalid University, Abha, Saudi Arabia
3. Department of Mathematics, Faculty of Science, Sohag University, Sohag, Egypt
4. Department of Mathematics, Faculty of Science, Islamic University of Madinah, Madinah, Saudi Arabia