When writing an academic paper, citing documents is an indispensable part, which can improve the credibility and academic nature of the paper, support your views and arguments, and avoid plagiarism and intellectual property infringement. If you don't know which documents are cited, there are several solutions:

1. Re-check the contents of the paper. Read every paragraph and main argument of the paper, try to recall what documents or books you read when writing, and record this information.

2. Check related notes or records. If you take notes or records on some contents during the writing of your thesis, you can check these notes or records to determine whether you have quoted relevant literature.

3. Use reference management tools. Reference management tools, such as EndNote and Mendeley, can help you effectively manage and track referenced documents and materials. If you use these tools, you can find the literature you cited through their retrieval function.

4. Ask a mentor or colleague. If you are not sure what documents you have quoted, you can consult your tutor, colleagues or other professionals, describe the theme and content of your paper to them, and see if they can recall the relevant documents you may have quoted.

5. Literature review or secondary inspection. If none of the above methods can determine which documents you cited, you may need to consult the documents again or check them again to see if there are other documents and materials related to your paper that have been missed.

In a word, it is a key step to establish which documents you have cited, and it is also an important aspect to ensure the academic and credibility of the paper. If you are not sure which documents are cited, you can use the above methods to find relevant documents and quote them accurately.