An, Yuan and Janssen, Jeannette and Milios, Evangelos E.. Characterizing and Mining the Citation Graph of the Computer Science Literature. In Knowl. Inf. Syst., (6) 664--678, Springer-Verlag New York, Inc., New York, NY, USA, Year 2004.

Small, Henry. Co-citation in the scientific literature: A new measure of the relationship between two documents. In Journal of the American Society for Information Science, (24) 4: 265--269, Wiley Subscription Services, Inc., A Wiley Company, Year 1973.