Credo Source Reference This link opens in a new windowCredo is an easy-to-use tool for starting research. Gather background information on your topic from hundreds of full-text encyclopedias and subject-specific titles, as well as 500,000+ images and audio files and over 1,000 videos. Links to other library online reference sites are included on the search results page and include Oxford University Press reference tools, links to our catalog, Britannica online, Salem History and many many more.