D. Bohus, and E. Horvitz. Proceedings of the 11th International Conference on Multimodal Interfaces and the 6th Workshop on Machine Learning for Multimodal Interfaces (ICMI-MLMI '09), Cambridge, MA, USA, page 31-38. (2009)
J. Allen, G. Ferguson, and A. Stent. Proceedings of IUI '01: 6th International Conference on Intelligent User Interfaces, Santa Fe, NM, USA, page 1-8. (2001)