1. Mathematics Department, Faculty of Science, Alexandria University, Alexandria, Egypt
2. Department of Mathematics and Engineering Physics, Faculty of Engineering, Mansoura University, Mansoura 35516, Egypt
3. Department of Basic Science, Faculty of Computers and Informatics, Ismailia 41522, Suez Canal University, Egypt
4. Mathematics Department, Faculty of Science, Mansoura University, Mansoura 35516, Egypt