1. superscript symbol: use superscript numbers to indicate references. Mark the cited places, and include the corresponding citation information in the reference list at the end of the article. For example, this is a quotation [1].

2. Embedded annotation method: directly embed the quoted literature information into the text without using superscript numbers. That is, use the author's name, publication year and other information to mark the cited places. For example, this is a reference (author, year) or (author, year, page number).

Which labeling method to use depends on academic norms, guidance documents or journal requirements. When writing a paper, the specific marking method should be determined according to the selected citation style (such as APA, MLA, Chicago, etc.). ) and follow the corresponding specifications.

No matter which labeling method is adopted, a complete list of references should be provided at the end of the paper, listing all the cited literature information. The format of the reference list should also follow the corresponding citation style specification.

In order to ensure the correct labeling of references, it is suggested to consult the Guide to Citation Style or the requirements of schools and periodicals, and label the reference information in strict accordance with the regulations.