1. Technical and Teacher Training School , Skikda , , Algeria
2. Faculty of Sciences and Technology, Department of Mathematics and Informatics , University of Souk Ahras , P.O. Box 1553, Souk Ahras, 41000 , Algeria
3. Applied Mathematics Lab, Faculty of Sciences , Department of Mathematics , University of Annaba , P.O. Box 12, Annaba 23000 , Algeria