1. School of Geographic Information and Tourism, Chuzhou University, Chuzhou, China
2. Research Center of Regional Economy, Henan University, Kaifeng, Henan, China
3. Department of Physics and Mathematics, School of Science and Technology, Nottingham Trent University, Nottingham, UK
4. Department of Geography, Environment, and Spatial Sciences, Michigan State University, East Lansing, MI, USA
5. Faculty of Science and Technology, Lancaster University, Lancaster, UK