1. Leng is Assistant Professor, Department of Statistics and Applied Probability, National University of Singapore, SG 117546, Republic of Singapore . Leng’s research is supported in part by NUS faculty research grants (R155-072-112, R155-000-080-112). Zhang is Assistant Professor, Department of Statistics and Finance, University of Science and Technology, Hefei, Anhui, 230026, China . Zhang’s research is supported by the NSF of China (No. 10671189, 11771204, 10801123). Pan is Professor, School of...