D. Salber, A. Dey, und G. Abowd. CHI '99: Proceedings of the SIGCHI conference on Human factors in computing systems, Seite 434--441. New York, NY, USA, ACM, (1999)
X. Shi, J. Zhu, R. Cai, und L. Zhang. KDD '09: Proceedings of the 15th ACM SIGKDD international conference on Knowledge discovery and data mining, Seite 777--786. New York, NY, USA, ACM, (2009)