1. Basic Science Department, Modern Academy for Engineering and Technology, Maadi 11585, Egypt
2. Department of Mathematics, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia
3. Physics Department Aldo Pontremoli, Universita degli Studi di Milano and I.N.F.N. Sezione di Milano, Via Celoria 16, 20133 Milan, Italy