It is possible, but you’ll have to have middleware in-between your GPT and your documents, for then to provide instructions to your GPT to always return the source URL, and then have an API that returns relevant context for you.
We’ve got existing clients doing this exact thing. Not because of citations, but rather because of maximum documents restrictions, where our middleware can handle tens of thousands of documents, while GPTs by default (I think) can only handle 20 (?)
Then we’ve got our own VSS database built from uploading documents, chopping up documents into pages, for then to insert download URL + page number into each training snippet, allowing the LLM to display links such as; “Download PDF and open page 123 to find the source for this answer” …
I don’t have any publicly available examples for you, since all our clients using this feature are either building custom GPTs or they’ve got their AI chatbot behind a firewall - But you get the idea …