Correspondence Chess/Vote chess

Rules question: Here, where it says "book and opening databases" are allowed for turn-based chess games, do the books include any opening books? I mean, are books that give annotated example games (every single one of my opening books does and as far as I know, there aren't any other types of opening books) allowed? I have never used any such book for neither vote chess nor correspondence chess for fear of breaking the rules, but I would be interested in picking up a tad bit of opening theory here and there by referencing books during the opening, if it is allowed.

So far, I have sometimes used chess.com's opening database (which the rules clearly say is ok). I think the database is fairly similar to a book, in that at the end of a line, there are often a handful of games in the database of that (main) line being played.

Thanks!

See site-playing-rules-a-guide-for-the-perplexed - scroll down to version 2.

Sweet, CC games can now encourage me to crack open my books--everything from opening to endgame.

Thanks for the clarification!