John Williams (art historian)
John W. Williams (February 25, 1928 – June 6, 2015) was an American art historian was an expert in Spanish medieval art. He was Andrew W. Mellon Professor of History of Art and Architecture end eventually Professor Emeritus, Medieval Art and Architecture, both at the University of Pittsburgh. Williams's best known work is "The Illustrated Beatus", a five-volume work. It was turned into the documentary film "Beatus: The Spanish Apocalypse".