1. School of Management Science and Engineering, Shandong University of Finance and Economics, Jinan, China
2. School of International Trade and Economics, Shandong University of Finance and Economics, Jinan, Shandong, China; KERMIT, Department of Data Analysis and Mathematical Modelling, Ghent University, Coupure links 653, 9000 Gent, Belgium
3. School of Economics, Shandong Women’s University, Jinan, China; School of Economics and Management, Southeast University, Nanjing, China
4. KERMIT, Department of Data Analysis and Mathematical Modelling, Ghent University, Coupure links 653, 9000 Gent, Belgium