Affiliation: | (1) Department of Mathematics, Xiamen University, Fujian, P.R. China;(2) Department of Physical Chemistry, The University of Trondheim, N-7034 Trondheim-NTH, Norway;(3) Department of Mathematics, Xinjiang University, Wulumuqi, P.R. China;(4) Siberian Branch of Russian Academy of Sciences, Institute of Mathematics, Novosibirsk, Russia |