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

HENRY SfAAU lrwtzt.le /or .%cntijfc [n/.rmatio. Philadelphia, Pemqdvmia 191W A now form of document coupling called co-citation is deffned as tfm frequency with which two documents are cifed togother. Th* co-citation frequency of two tcientiflc papers can b. determined by comporing fists of citing documents in the Science Citafien Index and cwn$ing identical enwics. Networks of co-cited poperi can be generated for speciffc scientific specialties, and an ●xample it drawn from the fiteratum of particle physics. Co-cikttion potferns are found to differ tie. nincantly from bibliographic coupling potterns, but to ogree generally with patterns of direct citation. ChIsiorI of co-cited papers provide a new way to study the wecialty structure of scietico. 7hay moy provida o new approach to indexing and to th. creation of SDI pro film. ● Introduction B1bliographm mtatmns m smentdic pap+rs have bmn used by s mnety of researched to estahbsb relat iomhp among documents, Both direct citat]on-the citing of an earlier document by a new document-and hiblio. gtaphic coupling-the aharmg of one or more references by Iwo documents-have received comidentble attention (f, S, 9, 4) A related measure, which bas been over. looked m earlier dkcu.wions, is co-citation Unhke blbbograpbic coupling wbicb links source documents, co-cit-a. tion hnks cited dmumcnts and IS, therefore, analogous to a measure of descriptor or word asomatlon (5), Tbe purpme of thm paper IS to define th~ new kind of “coupling” and to distingwh it from biblicgm.pbic coupling, using an actual example from the literature of pbys]cs Co+tatwn patternt are found to dfler mgnificantly fmm biblicgrapbic mupling patterns, but to agree generally with patterns of direct citation