Literature can be divided into first-class literature, second-class literature and third-class literature according to its content, nature and processing mode. This paper will introduce the classification of literature in detail and explain the definition of reference literature.

Original documents

Primary literature refers to the original literature created on the basis of the author's own research results, such as periodical papers, research reports, patent specifications, conference papers, etc.

The second article

Secondary literature is one of the retrieval tools such as bibliography, title record, introduction and abstract.

Three documents

The three documents are based on the first-level documents and the second-level documents. People usually refer to these documents as the results of "information research", such as reviews, thematic reviews, annual summaries of disciplines, progress reports, data manuals and so on.

refer to

References are the contents of other materials cited in your paper, such as data, concepts and other people's research results. You can't just write, you should write the exact source.