When you Shepardize a citation, you are looking for the citing references to your authority. In Shepard's citators, citing references are always found listed in a column below the cited reference. This is the body of law created by the judicial branch of government. Common law consists of principles and rules of action that have been created by judges in the course of writing opinions about litigated matters. A case, statute, regulation, or other legal authority that retains its value as precedent.
Legal authority is either primary or secondary.
A primary legal authority is a case, statute, regulation, or other authority supported by governmental power. A secondary legal authority is a treatise, law review article, or other source that comments on the law but is not supported by governmental power. A secondary authority may be used in an argument to persuade the court, however, and, if successful, the court may place its primary authority behind a secondary authority and adopt the secondary authority as precedent. Any written opinion, whether or not it is published in a reporter, may be referred to as a case by its case name. These citations are called parallel citations.