That would be indices, although I suspect indexes is acceptable.
I've looked at the Tarot Encyclopedia on a number of occasions, thinking it might be nice to have, but always come back to one thing -- why spring for these expensive books when a similar, much cheaper and more dynamic resource already exists? I'm talking, of course, about Aeclectic Tarot. What could the encylopedias offer that AE doesn't? And do the encylopedias have high quality color images of all the cards? And do they have reviews by a variety of experts that not only give their opinion but describe a number of aspects of the deck as well?
Aeclectic Tarot has completely satisfied my need for an excellent reference. And now AE is participating in creation of the Tarotpedia, a real, and currently free, encylopedia with all the cross-referencing you could possibly want.