The University Libraries often own different editions of a book or other resource. WorldCat UMD groups records for different editions and formats of a particular work to help users find generally the "best" record. This generally means that the item presented is a newer edition and held by the most libraries. While this may be an assumption, the goal is to help a variety of researchers find the best materials. Even if the book you find is checked out, you're also much more likely to be able to get the item from the many other libraries that hold the item in USMAI or the Big Ten because that item should be widely held
Of course, this method isn't for everyone. Sometimes a researcher needs a particular edition or even a unique edition of a book. If this is the case, you can turn off this grouping feature. When you perform a search in WorldCat UMD, you should find, on the left side of the screen, a column labeled "search tools". At the top of the column, uncheck the option to "Group related editions" to turn the grouping off. It will be directly below our logo.
Every record returned by your query will now display helping you find that particular item.
Another way to find other editions and formats is to access the Editions and Formats section of an item record. Each entry on the search results page which has grouped together other editions or formats of a work will display a link labeled "View all editions & formats".
Clicking on this link will direct you into the a section of the particular record allowing you to browse through the different editions and formats:
The grouping process is primarily performed using an algorithm informed by the Functional Requirements for Bibliographic Records commonly referred to as FRBR. The FRBR model posits a framework for understanding how different editions, translations, and formats of different kinds for works all relate to each other. If you are really interested, you can explore this document from the Library of Congress.