1. College of History and Tourism Culture, Inner Mongolia University, Hohhot 010020, China
2. Institute of Geographic Sciences and Natural Resources Research, Key Laboratory of Regional Sustainable Development Modeling, Chinese Academy of Sciences, Beijing 100101, China
3. University of Chinese Academy of Sciences, Beijing 100049, China
4. School of Tourism Sciences, Beijing International Studies University, Beijing 100024, China
5. Yungang Study College, Shanxi Datong University, Datong 037009, China