Online citators are useful for finding case history, statute history, parallel citations, and primary and secondary sources for specific topics. The top two legal databases use their own exclusive citator method: Westlaw uses the KeyCite method and LexisNexis uses the Shepard's Citation method. Our library no longer subscribes to LexisNexis, but it is important to be aware that both methods exist.
One of the best explanation guides is: What Is a Citator, Shepardizing, and KeyCiting?
