M. Coyle, and B. Smyth. IUI '07: Proceedings of the 12th international conference on Intelligent user interfaces, page 282--285. New York, NY, USA, ACM Press, (2007)
S. Stober, and A. N�rnberger. Proceedings of the International Conference on Adaptive Hypermedia and Adaptive Web-Based Systems (AH 2006), volume 4018 of LNCS, page 328 -- 332. Berlin / Heidelberg, Springer Verlag, (June 2006)