C. Marlow, M. Naaman, D. Boyd, and M. Davis. HYPERTEXT '06: Proceedings of the seventeenth conference on Hypertext and hypermedia, page 31--40. New York, NY, USA, ACM, (2006)
J. Zobel, A. Moffat, and R. Sacks-Davis. VLDB '93: Proceedings of the 19th International Conference on Very
Large Data Bases, page 290--301. San Francisco, CA, USA, Morgan Kaufmann Publishers Inc., (1993)