F. Carmagnola, F. Cena, O. Cortassa, C. Gena, and I. Torre. User Modeling 2007, volume 4511 of Lecture Notes in Computer Science, chapter 62, Springer Berlin Heidelberg, Berlin, Heidelberg, (2009)
M. Ames, and M. Naaman. CHI '07: Proceedings of the SIGCHI conference on Human factors in computing systems, page 971--980. New York, NY, USA, ACM, (2007)