M. Koch, A. Rancati, A. Grasso, и D. Snowdon. Proc. Human Computer Interaction International 99 Volume 2, стр. 417-421. London, Lawrence Erlbaum Publishers, (августа 1999)
J. Bardram, J. Bunde-Pedersen, и M. Soegaard. CHI '06: Proceedings of the SIGCHI conference on Human Factors in computing systems, стр. 211--220. New York, NY, USA, ACM Press, (2006)