1. Department of Mathematics, Faculty of Science, Cairo University, Giza, Egypt
2. Department of Mathematics, Faculty of Science, Taibah University, Madina, Saudi Arabia
3. Department of Mathematics, Gebze Technical University, Gebze, Kocaeli, Turkey
4. Department of Mathematics, Danang University, Danang, Vietnam
5. Department of Mathematics, The Ohio State University, Lima, Ohio, USA