I knew that they were working on computerizing the Index, but
I didn't think they were so far as getting it into something one
could "access" through a computer. (I'd love to be wrong on this!)
The Princeton Index of Christian Art is a card file, keyed to
illustrations on 5 x 8 1/2" cards. There is a copy at Dumbarton Oaks
in Washington D.C. that I've used, and copies at U.C.L.A., the
Vatican and Uppsala (?) that I've heard about.
The Princeton people might respond to inquiries, but only if
they're relatively contained, I believe.
Hope this helps,
Amelia Carr
