1. USTHB, Faculty of Mathematics, RECITS Laboratory, El Alia, Bab Ezzouar, Algiers, Algeria + Research Center on Scientific and Technical Information (CERIST), Ben Aknoun, Algiers, Algeria
2. USTHB, Faculty of Mathematics, RECITS Laboratory, El Alia, Bab Ezzouar, Algiers, Algeria + National Higher School of Mathematics, Mahelma, Sidi Abdellah, Algiers, Algeria