Shepard's Citations provides a list of all the authorities citing a particular case, statute, or other legal authority. The verb Shepardizing refers to the process of consulting Shepard's to see if a case has been overturned, reaffirmed, questioned, or cited by later cases. Although the name is trademarked, it is also used informally by legal professionals to describe citation providers in general, like Westlaw's KeyCite.
The Shepard's Citations Service provides a comprehensive case citation and treatment history to verify the validity of case law, statutes, agency opinions, and other legal documents.