Affiliation: | 1. Department of Mathematics and Institute for Advanced Study in Mathematics, Harbin Institute of Technology, Harbin 150001, PR China;2. Institute for Mathematical Sciences, Renmin University of China, Beijing 100872, PR China;3. Department of Natural Science in the Center for General Education, Chang Gung University, Guishan, Taoyuan 333, Taiwan;4. Community Medicine Research Center, Chang Gung Memorial Hospital, Keelung Branch, Keelung 204, Taiwan |