1. School of Finance and Statistics, East China Normal University, No. 500, Dong-Chuan Road, Shanghai 200241, China
2. School of Information Science and Technology, East China Normal University, No. 500, Dong-Chuan Road, Shanghai 200241, China
3. Department of Computer and Information Science, University of Macau, Av. Padre Tomas Pereira, Taipa, Macau