OAIster is a union catalog of digital resources. OAIster provides access to digital resources by "harvesting" their descriptive metadata (records) using OAI-PMH (the Open Archives Initiative Protocol for Metadata Harvesting).

Digital resources can range from an old-time advertisement of electric refrigerators (from the Library of Congress American Memory project) to Harriet Beecher Stowe memoirs (from the University of Michigan Digital Library Production Service Making of America collection).

Digital resources include items such as:

• digitized (i.e., scanned) books and articles
• born-digital texts
• audio files (e.g., wav, mp3)
• images (e.g., tiff, gif)
• movies (e.g., mp4, quicktime)
• datasets (e.g., downloadable statistics files)

The Oxford English Dictionary is the accepted authority on the evolution of the English language over the last millennium. It is an unsurpassed guide to the meaning, history, and pronunciation of over half a million words, both present and past. It traces the usage of words through 2.5 million quotations from a wide range of international English language sources, from classic literature and specialist periodicals to film scripts and cookery books.