1. Business School, Tianjin University of Finance and Economics, Tianjin 300222, P. R. China
2. School of Economics and Management, Zhejiang Normal University, Jinhua Zhejiang Province 321004, P. R. China
3. School of Management, Harbin Institute of Technology, Harbin, Heilongjiang Province 150001, P. R. China
4. Finance Office, Institute of Exploration Techniques, China Geological Survey, Tianjin 300300, P. R. China