1. Chengdu Library and Information Center, Chinese Academy of Sciences, Chengdu 610299, China
2. Department of Statistics, University of Michigan, Ann Arbor, MI 48109, USA
3. School of Business, Shandong University of Technology, Zibo 255000, China
4. Faculty of Management and Economics, Kunming University of Science and Technology, Kunming 650031, China
5. School of Business, Macau University of Science and Technology, Macau 999078, China
6. Department of Computer Science, Purdue University, West Lafayette, IN 47907, USA