1. School of Statistics, Southwestern University of Finance and Economics, Chengdu, Sichuan 611130, China
2. Guanghua School of Management, Peking University, Beijing 100871, China
3. Department of Statistical Science, Temple University, 1810 Liacouras Walk, Philadelphia, Pennsylvania 19122, U.S.A
4. Department of Biostatistics and Computational Biology, University of Rochester, 265 Crittenden Boulevard, Rochester, New York 14642, U.S.A