1. Shanghai University of Finance and Economics School of Statistics and Management, , 777 Guoding Road, Shanghai 200433, China
2. Department of Applied Mathematics, The Hong Kong Polytechnic University , Hung Hom, Kowloon, Hong Kong
3. Department of Mathematics and Statistics, York University , 4700 Keele Street, Toronto, Ontario M3J 1P3, Canada
4. School of Statistics and Management, Shanghai University of Finance and Economics , 777 Guoding Road, Shanghai 200433, China