1. * USTHB, Faculty of Mathematics, RECITS Laboratory , BP 32, El Alia, 16111 Bab Ezzouar , Algiers , ALGERIA , hbelbachir@usthb.dz
2. ** USTHB, Faculty of Mathematics, RECITS Laboratory , BP 32, El Alia, 16111 Bab Ezzouar , Algiers , ALGERIA
3. National Higher School of Mathematics , , Mahelma, 16093 Sidi Abdellah , Algiers , ALGERIA , ydjemmada@usthb.dz
4. *** University of Sopron, Institute of Mathematics , Sopron , HUNGARY
5. Associate member of USTHB, RECITS Laboratory , Algiers , ALGERIA