1. Basic Science Department, Modern Academy for Engineering and Technology, Maadi 11571, Egypt
2. Department of Mathematics, Faculty of Science, Fayoum University, Fayoum 63541, Egypt
3. Department of Pure Mathematics, University of Calcutta, Ballygaunge Circular Road, Kolkata 700019, India
4. Physics Department Aldo Pontremoli, Universita degli Studi di Milano and I.N.F.N. Sezione di Milano, Via Celoria 16, 20133 Milan, Italy
5. Department of Mathematics, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia