M. Cavaretta, and K. Chellapilla. Proceedings of the Congress on Evolutionary
Computation, 2, page 1330--1337. Mayflower Hotel, Washington D.C., USA, IEEE Press, (6-9 July 1999)
R. Kumar, A. Tomkins, and E. Vee. WSDM '08: Proceedings of the international conference on Web search and web data mining, page 129--138. New York, NY, USA, ACM, (2008)