Brahim Mansoul
Laboratory of Applied Mathematics, University Mohamed Khider P.O. Box 145, Biskra 07000, Algeria
Abdelkarim Digheche
Laboratory of Applied Mathematics, University Mohamed Khider P.O. Box 145, Biskra 07000, Algeria
Adel Chala
Laboratory of Applied Mathematics, University Mohamed Khider P.O. Box 145, Biskra 07000, Algeria