1. CRMEF, Rabat-Salé-Kénitra, Avenue Allal El Fassi, Bab Madinat Al Irfane, B.P 6210, 10000 Rabat, Morocco
2. Laboratory of Mathematics and Applications, Faculty of Sciences and Technologies, University Hassan II Casablanca, Mohammedia, Morocco
3. Laboratory of Algebra, Analysis and Applications (L3A) Hassan II University of Casablanca, Faculty of Sciences Ben M’Sik, Avenue Cdt Driss El Harti, B.P 7955, Sidi Othmane, Casablanca, Morocco