1. College of Continuing Education and Open College, Guangdong University of Foreign Studies, Guangzhou, 510420, China
2. The Faculty of Economics, Guangdong University of Finance and Economics, Guangzhou, 510320, China
3. Modern Business and Management Department, Guangdong Construction Polytechnic, Guangzhou, 510440, China
4. School of Mathematics and Statistics, Central South University, Changsha, 410083, China