T. Upstill, N. Craswell, and D. Hawking. Proceedings of the Australasian Document Computing Symposium, ADCS2003, page 31--40. Canberra, Australia, (December 2003)
D. Nettleton, L. Calderon-Benavides, and R. Baeza-Yates. LA-WEB '06: Proceedings of the Fourth Latin American Web Congress (LA-WEB'06), page 209--219. Washington, DC, USA, IEEE Computer Society, (2006)