The Turabian and Chicago manuals offer extensive advice about all sorts of formats. Please contact a librarian if you would like to consult about a format that is not covered by this guide. You can reach us at askalibrarian@ambs.edu.
From time to time, you will have incomplete citation information. The best advice is to offer all the information you have available rather than avoiding use of the source or not citing it at all.
Generative Artificial Intelligence use must be cited, or it is considered plagiarism at AMBS. Here's an example:
OpenAI. "Chat with GPT-3.5 on Citing in Turabian Format." ChatGPT, April 24, 2023. https://www.openai.com/chat.
Whenever possible, do your best to locate the original source of information rather than referring to something as cited by someone else. This ensures the accuracy of the information.
If it's not possible to trace back the citation, there is a format to cite something as cited in another source.
You list the citation the other author referred to first, then say "quoted in" and list the citation you consulted.