I'm an undergraduate. I sent two emails to professors regarding potential research work. Both responded positively, which I didn't expect, and I started work with one of the profs last term. As for the other, I think his work is incredibly interesting but I simply don't have the time for two research projects at once. However, I would really like to work with him eventually.
How can I tell the other professor that I'm too busy this quarter but would like to work with him at some point in the future? It seems a bit awkward to mention the other professor so I'm not sure how to explain it.