Category talk:Expanded universe

Do we have an official line on what is EU? I'm thinking specifically of the prequels - I've heard people say that they are/aren't EU at different places - the prequel pages themselves don't have the EU icon at the top, but Tomas Sherek does, presumably for his part in the S4 prequel. And they're not in the EU section of the appearances template. I'd like to add an explanation of what is EU to the intro line of this category page, as I'm a tad unclear myself--Acer4666 18:59, April 26, 2011 (UTC)