1. College of Mathematics and Statistics, Institute of Statistical Sciences, Shenzhen University, Shenzhen, China
2. Department of Computer Science, and Institute of Computational and Theoretical Studies, Hong Kong Baptist University, Kowloon Tong, Hong Kong
3. School of Statistics, Capital University of Economics and Business, Beijing, China
4. Department of Mathematics, Hong Kong Baptist University, Kowloon Tong, Hong Kong