[1] Univ Yaounde I, Dept Phys, Higher Teachers Training Coll, Nonlinear Phys & Complex Syst Grp, POB 47, Yaounde, Cameroon
[2] Univ Douala, Dept Phys, Grp Nonlinear Phys & Complex Syst, Pure Phys Lab, POB 24157, Douala, Cameroon
[3] Bangabandhu Sheikh Mujibur Rahman Sci & Technol U, Dept Math, POB 8100, Gopalganj, Bangladesh
[4] Fotso Victor Univ Inst Technol, Dept Telecommun & Network Engn, LAIA, POB 134, Bandjoun, Cameroon