基金the National Natural Science Foundation of China(10431010)the MOE Project of Key Research Institute of Humanities and Social Sciences in Universities (05JJD910001)Center for Applied Statistics of Renmin University of China
基金Supported by the National Natural Science Foundation of China(10431010),theMOE Project of Key Research Institute of Humanities and Social Sciences in Universities(05JJD910001)and Center for Applied Statistics of Renmin University of China