How can I cite a previously given, unavailable talk without self-plagiarism In University, I was part of a philosophy reading group where people would occasionally give talks about their on-going research. Several years ago I gave one such talk, and presented original and new ideas that were never published or presented in a more formal setting, although the ideas were also presented in a term paper I wrote that same year. There is no public record of the contents of the talk, or even that that talk happened.

Now I am in a situation where I wish to reference that same idea in a research paper. It is outside the scope of the current paper paper to present those ideas as a new thing, but it would be something that would be appropriate to reference as existing.

How would I do that? I could get a DOI for the talk and reference it using that, but I would feel weird about referencing an unavailable talk that I gave, as it would feel like citation padding. This is doubly true since it is early in my career. I could write up a summary of the talk and put it on a publicly available repository, but I’m not sure if that’s a thing that is done. Are there other options?
I think the right action hinges on this point:


  It is outside the scope of the current paper paper to present those ideas as a new thing, but it would be something that would be appropriate to reference as existing.


It seems like you want to reference your past work because it is out of the scope of the new work and yet still relevant. If this is correct, then referencing the talk will not help the reader, who may (or may not) need to know about the past idea, concept, or whatever it was. Therefore your only option would be to publish the ideas in some form (paper, blog, etc.) or explain them briefly in the new paper.

If you simply want to show the history of your ideas, but it is not important, then I would leave out and simply acknowledge whoever helped you out.

If you are worried primarily about self-plagiarism, I do not see how not citing a non-published talk, that you yourself gave, is much different from not citing some thoughts you had in your head two years ago. It is a bit different, but not to the extent that it would constitute self-plagiarism, which is really about making it clear what is and what is not new in a paper as it is assessed for novelty during peer-review.