1. citation format: documents cited twice need to use APA, MLA, Chicago or other academic writing formats. These formats have detailed rules to guide you how to format references.
2. Direct citation and indirect citation: For documents directly cited twice, the original author's name and publication year should be included in the citation. If the literature is only cited twice indirectly, only the original author's name and publication year are required.
3. Information in brackets: When the literature cited twice is quoted, additional information can be provided in brackets, such as page numbers or chapter titles. This can help readers understand your quotation better.
4. Reference list: In your reference list, you need to list all references according to your citation format. For documents cited twice, you should indicate whether it is the first citation or the second citation in brackets.
5. Use citation management tools: There are many citation management tools, such as EndNote, Zotero and Mendeley, which can help you manage and format your citations. These tools can automatically generate the correct citation format for you and help you keep track of your references.
6. Avoid over-quoting: Although over-quoting is important, it may make your article look confusing and difficult to read. You should only quote those documents that have a direct impact on your research.
Generally speaking, you need to follow certain rules and formats to mark the documents cited twice in English papers, and you need to use appropriate tools to help you manage your own citations. Correctly marking your quotations can ensure that your research is transparent and traceable, and at the same time avoid plagiarism.