1. School of Economics and Management, Inner Mongolia University, Hohhot 010020, China
2. Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China
3. Department of Geography, School of Geography and Information Engineering, China University of Geosciences, Wuhan 430078, China
4. College of Public Administration, Nanjing Agricultural University, Nanjing 210095, China
5. School of Economics and Management, Beijing University of Technology, Beijing 100124, China