1. School of Economics and Finance, Chongqing University of Technology, Chongqing 400054, China
2. School of Economics and Business Administration, Chongqing University, Chongqing 400045, China
3. School of English, Beijing International Studies University, Beijing 100024, China
4. Energy Institute, University College London, London WC1E 6BT, UK
5. School of Graduate Studies, Lingnan University, Hong Kong, China