Gray literature is a kind of literature between "black literature" (such as various internal documents) which is not published publicly and has the nature of confidentiality and "white literature" which is published publicly. It will not be published publicly, but it will not be strictly confidential. Although it is troublesome to obtain, it can be obtained after all.

Dissertations are divided into undergraduate dissertations, master's dissertations, doctoral dissertations and postdoctoral exit reports, while the general focus is on master's and doctoral dissertations.

The three elements of a dissertation are the degree level, the awarding unit and the tutor's name, all of which are indispensable. The characteristics of the paper are uneven quality, long length, originality, novelty, detailed content and complete system.

There are two main types of databases containing master's and doctoral dissertations in China. One is the database led by relevant national institutions, such as China National Digital Library and NSTL National Science and Technology Library, which is the most authoritative. Second, various third-party databases, such as CNKI, Wanfang, CADAL, Huayi Taiwan Province Academic Degree Library, and Taiwan Province Master's and Doctoral Thesis Knowledge Value-added System.