You can do it the same way human does: recall a fact from memory, and then search to identify a citation. The citation isn't "here's why I think this" but instead "here's where you can verify this".
It feels lazy that this isn't built into the harness in some adversarial citation review checkbox.
Also the questions LLMs ask are so inhuman. It's like it's some contrarian trying to win an argument over getting an answer.