Start research in the online Library Catalog . Use a bibliography or index to identify articles in journals. The Dictionary of Art Online and The Dictionary of Art New York, Grove's Dictionaries, 1996.
Many articles have brief bibliographies appended.
Encyclopedia of World Art . A Topical Dictionary . Encyclopedia of Comparative Iconography . An alphabetically-arranged set of essays on major themes in art throughout the ages, with lists of selected artworks which utilize each theme, and good bibliographies. Great for comparative studies.