1. School of Information Science & Technology, East China Normal University No. 500, Dong-Chuan Road, Shanghai 200241, China
2. Department of Computer and Information Science, University of Macau, Avenue Padre Tomas Pereira, Taipa 1356, Macau SAR, China
3. Faculty of Engineering, Multimedia University, Selangor Darul Ehsan, 63100 Cyberjaya, Malaysia
4. Department of Mathematics, University of Salerno, Via Ponte Don Melillo, 84084 Fisciano, Italy
5. Department of Mathematics, University of Rome, la Sapienza Piazzale Aldo Moro, 00185 Rome, Italy