1. Department of Statistics and Operations Research, University of North Carolina,Chapel Hill, North Carolina 27599, USA
2. School of Mathematics and Statistics, Jiangxi Normal University, Nanchang, Jiangxi 330022, People’s Republic of China
3. Department of Mathematics, Faculty of Science and Technology, University of Macau Av. Padre Tomás Pereira, Taipa Macau, China
4. UMacau Zhuhai Research Institute, Zhuhai, China