Primary literature is the original literature, secondary literature is the product of processing and sorting the primary literature, and tertiary literature is the product of comprehensive and generalization after extensive and in-depth analysis and research of primary literature and secondary literature. .
In information science, different terms are often used to describe different levels and properties of documents. Primary documentation contains original documentation of inventions and new insights. This includes journal articles, research reports, patent specifications, conference papers, theses, technical standards, etc. Secondary documents describe the external characteristics of primary documents, such as title, author, source, etc., and compress the document content into the form of introduction, abstract or abstract. The purpose of secondary literature is to organize and classify primary literature to make it easier to find and use. Tertiary literature is the product of a comprehensive summary of primary literature and secondary literature after extensive and in-depth analysis and research. It is the result of comprehensive research and summary of relevant literature. The three literatures include reviews, topic reviews, subject annual summaries, progress reports, data manuals, progressive publications, and literature guides.