Affiliation: | 1. National Advanced School of Engineering, University of Yaounde I, P.O. Box 8390, Cameroon;2. Department of Physics, Faculty of Science, University of Yaounde I, P.O. Box 812, Cameroon;3. Centre d’Excellence en Technologies de l’Information et de la Communication (CETIC), University of Yaounde I, Yaounde P.O.Box 812, Cameroon;4. The Abdus Salam International Centre for Theoretical Physics (ICTP), Strada Costiera, Trieste 11-I-34151, Italy |