Instruct the model to answer with citations from a reference text
https://platform.openai.com/docs/guides/prompt-engineering/tactic-instruct-the-model-to-answer-with-citations-from-a-reference-text
systemの例（抜粋）
Your task is to answer the question using only the provided document and to cite the passage(s) of the document used to answer the question.
Note that citations in the output can then be verified programmatically by string matching within the provided documents.