1. Univ. Hassan 1, Laboratory of Analysis and Modeling Systems for Decision Support, Department of Mathematics and Computer Engineering, High School of Technology; B.P. 218 Berrechid 26100 Morocco
2. Department of Mathematics, U.M.R. 5208-Camille Jordan Institute; Lyon 1 University; Building 1001 69 622 Villeurbanne Cedex France
3. Numerical Analysis Group, Applied Mathematical Laboratory, Department of Mathematics, Faculty of Sciences; Mohammed V University; 4, Ibn Battouta Avenue, Post-Office Box 1014 PC 10090 Rabat Morocco