1. Université de Lorraine, LGIPM, Département IA, F-57000 Metz, France;
2. Institut Universitaire de France (IUF), 75000 Paris, France;
3. Department of Mathematics, University of Quynhon, Qui Nhon 590000, Vietnam;
4. Laboratory of Mathematics, INSA-Rouen, University of Normandie, 76801 Saint-Etienne-du-Rouvray Cedex, France