1. School of Economics and Management, Shijiazhuang Tiedao University, Shijiazhuang, People's Republic of China
2. School of Economics and Management, Beijing University of Chemical Technology, Beijing, People's Republic of China
3. School of Mathematics and Physics, Hebei University of Engineering, Handan, People's Republic of China
4. Department of Computer Science, Aberystwyth University, Aberystwyth, UK