Co‐citation in the scientific literature: A new measure of the relationship between two documents

Abstract A new form of document coupling called co‐citation is defined as the frequency with which two documents are cited together. The co‐citation frequency of two scientific papers can be determined by comparing lists of citing documents in the Science Citation Index and counting identical entries. Networks of co‐cited papers can be generated for specific scientific specialties, and an example is drawn from the literature of particle physics. Co‐citation patterns are found to differ significantly from bibliographic coupling patterns, but to agree generally with patterns of direct citation. Clusters of co‐cited papers provide a new way to study the specialty structure of science. They may provide a new approach to indexing and to the creation of SDI profiles.