G. Abowd, A. Dey, P. Brown, N. Davies, M. Smith, und P. Steggles. Proceedings of the 1st international symposium on Handheld and Ubiquitous Computing, Seite 304--307. London, UK, Springer-Verlag, (1999)
A. Popescul, L. Ungar, D. Pennock, und S. Lawrence. 17th Conference on Uncertainty in Artificial Intelligence, Seite 437--444. Seattle, Washington, (August 2001)
G. Karypis. Proceedings of the tenth international conference on Information and knowledge management, Seite 247--254. Atlanta, Georgia, USA, ACM Press, (2001)