P. Dolog, N. Henze, W. Nejdl, and M. Sintek. Proceedings of the 13th International World Wide Web Conference on Alternate Track Papers &Amp; Posters, page 170--179. New York, NY, USA, ACM, (2004)
P. Chirita, S. Costache, W. Nejdl, and S. Handschuh. WWW '07: Proceedings of the 16th international conference on World Wide Web, page 845--854. New York, NY, USA, ACM, (2007)