Okay, I have a made up acronym in my book which is A-B (yes with the dash in there). If I wanted to pluralize it, would I put an apostrophe s, so that it would read A-B's? I'm asking because I recently read in a book where someone wrote "yeses" and "noes". I found this to be so awkward looking. I would think it's yes's and no's. Is there an official rule?