S. Bao, G. Xue, X. Wu, Y. Yu, B. Fei, and Z. Su. WWW '07: Proceedings of the 16th international conference on World Wide Web, New York, NY, USA, ACM Press, (2007)
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)