1. L3A Laboratory, Department of Mathematics and Computer Sciences, Faculty of Sciences Ben M'sik, University of Hassan II Casablanca, Morocco
2. Laboratory of Mathematics and Applications, Faculty of Sciences and Technologies, Mohammedia, University Hassan II Casablanca, Morocco
3. LASMA Laboratory, Department of Mathematics, Faculty of Sciences Dhar El Mahraz, University Sidi Mohamed Ben Abdellah, Fes, Morocco