Background sources such as, but not limited to, dictionaries and encyclopedias provide context for your topic or even help you choose one. Researchers use them when they need:
Encyclopedia entries and images for art. Includes Grove Art Online, the Encyclopedia of Aesthetics, The Oxford Companion to Western Art, and The Concise Oxford Dictionary of Art Terms. Coverage: varies.
Encyclopedia, dictionary and biographical entries from hundreds of sources for most subject areas. It includes images, diagrams, maps and photos, and audio pronunciation files and sound clips. Coverage 2000 – present.