1, document name approach: use article title, publication title and book title as search marks to find relevant documents.

2. Author method: Use the names of known authors (including group names) as the method of searching documents.

3. Subject method: a method of searching according to the theme of the literature (main concepts, research objects, issues and concerns, etc.). ).

4. Classification method: Using the classification index in the retrieval tool as the retrieval mark is a method of consulting literature.