Affiliation: | (1) Department of Mathematics, National Taiwan Normal University, 88, S-4, Ting Chou Road, Taipei, 117, Taiwan;(2) Université Paul Cézanne Aix-Marseille III, LATP (UMR CNRS 6632) F.S.T, Avenue Escadrille Normandie-Niemen, F-13397 Marseille Cedex 20, France |