1. Guanghua School of Management, Peking University, Beijing 100871, China;
2. Department of Statistics and Actuarial Science, The University of Hong Kong, Hong Kong;
3. Naveen Jindal School of Management, The University of Texas at Dallas, Richardson, Texas 75080;
4. Department of Mathematics, Statistics and Insurance, School of Decision Sciences, The Hang Seng University of Hong Kong, Hong Kong;
5. Department of Statistics, The Chinese University of Hong Kong, Hong Kong