L. Backstrom, D. Huttenlocher, J. Kleinberg, and X. Lan. KDD '06: Proceedings of the 12th ACM SIGKDD international conference on Knowledge discovery and data mining, page 44--54. New York, NY, USA, ACM Press, (2006)
D. Liben-Nowell, and J. Kleinberg. CIKM '03: Proceedings of the twelfth international conference on Information and knowledge management, page 556--559. New York, NY, USA, ACM Press, (2003)
B. Wellman, and M. Gulia. chapter Net Surfers Don't Ride Alone: Virtual Communities as Communities, University of California PressCalifornia Press, Berkeley, CA, (1997)