1. LME, Université Mohammed 1er, Faculté des Sciences, 60000 Oujda, Morocco
2. ENSAO, EMCS, Complexe Universitaire, B. P. 669, 60000 Oujda, Morocco
3. LAGA, Université Paris 13, 99, Avenue J. B. Clément, 93430 Villetaneuse, France
4. Department of Engineering Science, University of Oxford, Parks Road, Oxford OX1 3PJ, UK