D. Cox, V. Kindratenko, and D. Pointer. UbiComp 2003: Ubiquitous Computing, volume 2864 of Lecture Notes in Computer Science, Springer, Berlin / Heidelberg, (2003)
T. Rattenbury, N. Good, and M. Naaman. SIGIR '07: Proceedings of the 30th Annual International ACM SIGIR Conference on Research and Development in Information Retrieval, page 103--110. New York, NY, USA, ACM Press, (2007)