1. Books: Basic geography textbooks and reference books are important references. For example, the principles of geography and geographic information system.
2. Academic journals: The research results of geography are usually published in various academic journals, such as Journal of Geography, Geographical Research and Geographical Science.
3. Academic report: Many geographical research results will be published in the form of reports, which is also an important reference. For example, reports issued by the US Geological Survey (USGS) and the US Environmental Protection Agency (EPA).
4. Conference papers: The research results of geography will also be published in various academic conferences, and these conference papers are also important references. For example, the conference documents of the International Geographical Union (IGU) and the International Association of Remote Sensing (IRRS).
5. Dissertations: Postgraduates' dissertations usually contain in-depth research, and these papers are also important references.
6. Network resources: There are a lot of geographical resources on the Internet, including online databases, e-books and academic websites. For example, GoogleScholar, JSTOR, GeoScienceWorld, etc.
7. Maps and data: Geographical research needs a lot of maps and data, which are also important reference materials. For example, maps and data released by the US Geological Survey (USGS) and the US Environmental Protection Agency (EPA).
8. Policy documents and reports: Geographical research also needs to consider policy factors, so policy documents and reports are also important references. For example, reports issued by the United Nations Environment Programme (UNEP) and the World Bank.