M. de Gemmis, P. Lops, G. Semeraro, and P. Basile. RecSys '08: Proceedings of the 2008 ACM conference on Recommender systems, page 163--170. New York, NY, USA, ACM, (2008)
J. Fogarty, R. Baker, and S. Hudson. GI '05: Proceedings of Graphics Interface 2005, page 129--136. School of Computer Science, University of Waterloo, Waterloo, Ontario, Canada, Canadian Human-Computer Communications Society, (2005)
R. Jäschke, F. Eisterlehner, A. Hotho, and G. Stumme. RecSys '09: Proceedings of the 2009 ACM Conference on Recommender Systems, New York, NY, USA, ACM, (2009)(to appear).