1. Department of Mathematical and Statistical Sciences, University of Alberta, Alberta, Canada
2. Yunnan Key Laboratory of Statistical Modeling and Data Analysis, Yunnan University, Kunming, People's Republic of China
3. Department of Statistics, University of Warwick, Warwick, UK
4. School of Mathematics, Statistics and Physics, Newcastle University, Newcastle upon Tyne, UK
5. School of Mathematics, Statistics and Mechanics, Beijing University of Technology, Beijing, People's Republic of China