An excellent source for books on ALL military subjects is here:
www.motorbooks.co.uk they are based just by Covent Garden in London as you cut through the alleys from Leicester Square, I have been in there many times, well worth checking out for their superb range of books.
They cover just about everything you need for this whole site regardless of what type of models you do, the list on line doesn't really do justice to them...I have spent hours in this shop alone....and spent a few bob too..!!!
Regards.......Mark.