J. Freyne, R. Farzan, P. Brusilovsky, B. Smyth, and M. Coyle. IUI '07: Proceedings of the 12th international conference on Intelligent user interfaces, page 52--61. New York, NY, USA, ACM Press, (2007)
A. Hotho, R. Jäschke, C. Schmitz, and G. Stumme. The Semantic Web: Research and Applications, 3rd European Semantic Web Conference, ESWC 2006, Budva, Montenegro, volume 4011 of Lecture Notes in Computer Science, page 411-426. Berlin / Heidelberg, Springer, (11-14 June 2006)