1. School of Economics, Qingdao University, Qingdao, China
2. School of Foreign Language Education, Qingdao University, Qingdao, China
3. School of Marxism, East China University of Political Science and Law, Shanghai, China
4. Department of Economics, University of Sheffield, Sheffield, UK
5. College of Engineering and Applied Sciences, Stony Brook University, New York, NY, USA