Affiliation: | 1. College of Mathematics and Econometrics , Hunan University , Changsha, Hunan 410082, PRC;2. Department of Mathematics , Guangdong University of Finance , Guangzhou, Guangdong 510521, PRC luoguimei@126.com;4. College of Mathematics and Econometrics , Hunan University , Changsha, Hunan 410082, PRC;5. Department of Mathematics , Guangdong University of Finance , Guangzhou, Guangdong 510521, PRC |