1. Author-publication year system: This is one of the most common citation formats, which is used to list the author and publication year of a document. For example, Smith, J.(2005).
2. Sequential coding system: This format numbers the documents according to the order in which they appear in the paper. For example, (1), (2), (3) and so on.
3. Author-date system: This format puts the author and publication date of the document together. Such as Smith, J.&; Johnson, K.(2005).
4. Footnotes and endnotes: Footnotes and endnotes are used to add additional information or comments at the bottom or end of the article. They are usually used to explain terms, provide data sources or refer to other documents.
5. Note in brackets: When citing documents, the author, publication year and other information can be indicated in brackets. For example, according to Smith's research (2005),
6. List of references: The list of references is the place where all the cited documents are listed at the end of the paper. Usually arranged in a specific citation format, such as APA, MLA or Chicago.
7. Superscript and Subscript: Superscript and Subscript are used to represent specific concepts or variables. For example, x_ stands for the square of x.