1. Hansheng Wang is Associate Professor, Department of Business Statistics & Econometrics, Guanghua School of Management, Peking University, Beijing, P. R. China, 100871 . Yingcun Xia is Associate Professor, Department of Statistics and Applied Probability, National University of Singapore, Singapore, 117546 . The authors thank the joint editors, the associate editor, and two referees for their careful reading and constructive comments, which led to substantial improvements in the manuscript. They are also...