1. School of Economics and Finance, South China University of Technology, Guangdong 510006, China
2. School of Mathematics and Computer Science, Chongqing College of International Business and Economics, Chongqing 401520, China
3. School of Mathematics and Statistics, Guilin University of Technology, Guangxi 541000, China
4. Applied Statistics Institute, Guilin University of Technology, Guangxi 541000, China