Getting beyond this is a tricky dark art. There isn't any simple there. There's nowhere to put an if statement.
Ask them to give you some literature recommendations on something it has explained to you. You'll get plenty of plausible sounding papers that don't exist.
Humans know to some extent why they know (read it in a text book, colleague mentioned it). LLMs don't seem to.
I can’t tell you the date of every time I clip my toenails, but if I had to could remember it.
When you ask an LLM to tell you the height of Mount Everest, it clearly has a map of mountains to heights, in some format. Using exactly the same mapping structure, it can remember a source document for the height.
This argument comes up many times “people don’t do this” - but that is a question of frequency, not whether or not people are capable.
But also, can you give an example where an LLM with access to the Internet can find a primary source?
I don't think learning to refer to sources is something inherently impossible for LLMs, but it is very different to the kind of implicit knowledge they seem to excel at.
I think perhaps your description is more succinct