Over at Splendor Veritatis Christopher Gray made available scans of several Cistercian chant books. It's a very valuable resource, as these books are very hard to find elsewhere.
Because the site is just a simple photo-gallery, to find some particular occasion or chant is usually quite a hard task. This humble site attempts to alleviate it by providing a table of contents for each of the books.
For now there is only a WIP index of the 1947 Trappist Antiphonale, because it's the item most interesting for the author.