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)
M. Araki, and Y. Funakura. Spoken Dialogue Systems for Ambient Environments: Second International Workshop, IWSDS 2010, Gotemba, Shizuoka, Japan, volume 6392 of Lecture Notes in Artificial Intelligence, Springer, Berlin, (2010)