Affiliation: | 1.Analysis, P.D.E, Spectral Geometry, Lab. M.I.A.-S.I., CeReMAR, Department of Mathematics, Faculty of Sciences, Mohammed V University in Rabat, Rabat, Morocco ;2.Analysis, P.D.G, Spectral Geometry. Lab. M.I.A.-S.I., CeReMAR, Department of Mathematics, Faculty of Sciences, Mohammed V University in Rabat, P.O. Box 1014, Rabat, Morocco ;3.Faculty of Law, Economics and Social Sciences, Ibn Zohr University, Agadir, Morocco ; |