Let's say I'm writing a set of notes on a specialized topic, based off of notes from a deceased professor, who he himself had a disclaimer that his notes (theorems, proofs, ideas) were not properly attributed and cited, due to time constraints. What should I do then, if I plan to distribute my notes / post it on a website? Should I have a disclaimer of my own?
Citing notes is unusual. Assuming the theorems were original work by the professor¹, I would either:
- Cite it as (P. Rofessor, personal communication),
- or add a note to the acknowledgements describing the situation.
My preference would be the second alternative, because the first alternative may imply that P. Rofessor has agreed to transferring this information to you, and he hasn't (unless he told you before his death, or stated it in his will?).
Whatever you do, the most important is that you make it unambiguously clear that the relevant notes are not your original work — otherwise you risk accusations of plagiarism / theft.
¹If they aren't, Johanna's answer applies.