The traditional way to find references is through the library, and the books in the library are the main way to find traditional references. Compared with other ways, it has the advantages of convenience and practicality.

2. HowNet

China Knowledge Network (CNKI) is the authoritative source of online literature. Most colleges and universities have cooperated with China HowNet, so they can enjoy the treatment of downloading documents for free at school.

Like HowNet, there are Wanfang Database, VIP Periodical, Baidu Academic and so on.

3. Google Academic Google Academic

This is the most commonly used by many people. Compared with other paper retrieval websites, Google has rich academic free resources.

4. Scientific guidance

It is the largest online scientific research collection in the world, with strong professionalism.