The journals are fully indexed by title, author, and subject. Auction Houses Christie's International includes sales information, lists of auction catalogues, and other information about the company. Sotheby's web site includes sections for Collecting , Catalogues , and Services . The Art Price Guide at icollector has sales information going back to 1987. The Kovels have an online price guide database that can be browsed or searched.
Registration is required, but free.
If worse comes to worst, check Ebay and see what others are asking for the same or similar items. The Great Buildings Collection is a site listing major architects and buildings, their locations, type of construction, and bibliographic references for more information. Some have photographs and 3D models. Offers articles, links to other web sites, recommended reading, and more. Copyright Office has application forms, announcements, and other pertinent information about copyright.