② Tsinghua Library has a full-text database of national excellent doctoral and master's dissertations and important national conference papers, which is also an important source of information for writing graduation thesis;
③ The three major chinese numerals libraries (superstar, founder and scholar) are important sources of literature information;
(4) Using two search engines can help you expand your thinking range and guide you to find new literature information resources.
⑤ What should I do if I can't find enough documents? You can use snowball method to search, that is, use the references after the found documents to expand the search scope. Tsinghua Library's "China Journal Citation-Full-text Link Record Library" is also a powerful tool to help you realize "snowball search";