The basic principle underlying the organization of any library is to describe the documents it contains so that they may be located. All libraries create sets of records which describe the documents in their collections. Catalogs are sets of records to documents that share a location. Indexes are sets of records to documents that share some other attribute (generally subject matter). Below are among the most comprehensive and significant indexing databases for legal literature and scholarship. Further guidance may be found at the Mabie Law Library.