1. Saudi Center for Theoretical Physics, Dhahran, Saudi Arabia
2. Physics Department, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia
3. Physics Department, College of Science, King Faisal University, P. O. Box 380, Alahsa 31982, Saudi Arabia
4. Theoretical Physics Group, Faculty of Sciences, Chouaïb Doukkali University, P. O. Box 20, 24000 El Jadida, Morocco