1. School of Tourism & Research Institute of Human Geography, Xi’an International Studies University, Xi’an 710128, China
2. School of Geography and Tourism, Shaanxi Normal University, Xi’an 710119, China
3. State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
4. School of History and Archives, Yunnan University, Kunming 650091, China