1. Direct insertion method: When the document is quoted in the text of the paper, the document information can be directly inserted at the quotation. For example, "According to Smith's research (20 10), ……", in which "Smith's research (20 10)" is directly inserted into the literature information.

2. Bracket method: When quoting documents in the text of the paper, you can also enclose the document information in brackets. For example, "... (Smith, 20 10) indicates ...", where "(Smith, 20 10)" is the document information using brackets.

3. Superscript method: Superscript can also be used when citing documents in the text of the paper. For example, "According to Smith's research [1], ……", where "[1]" is the document information using superscript.

4. Footnote method: Footnotes can also be used for marking when citing documents in the text of the paper. For example, "According to Smith's research [1], ……", where "[1]" is the document information using footnotes.

It should be noted that when adding references, it is necessary to ensure the accuracy and completeness of literature information, and at the same time, it is necessary to follow the citation norms and requirements of this field or journal. When writing a paper, you need to carefully consult the relevant academic norms and requirements and quote them according to the norms. At the same time, it is necessary to list all the cited documents in the reference list, so that readers can refer to the original text and verify the source of the paper.