Rookwood is pictured in many books, but get one that illustrates its marks, such as Kovels’ American Art Pottery: The Collector’s Guide to Makers, Marks, and Factory Histories , by Ralph and Terry Kovel. Just Art Pottery sells Rookwood on the Internet ( www.justartpottery.com ), and you can preview examples up for auction at Cincinnati Art Galleries and Craftsmen Auctions ( www.cincinnatiartgalleries.com ; www.craftsman-auctions.com ).