What is bibliographic coupling?

Bibliographic coupling links two papers that cite one or more of the same sources. The more references they share, the more likely they work on the same problem. Because it depends only on a paper’s own reference list, it relates new papers immediately, before anyone has cited them.

Coupling is fixed once a paper is published; co-citation grows over time.

Together they give a good map: coupling for recent work, co-citation for foundations.