K. Kamei, K. Shinozawa, T. Ikeda, A. Utsumi, T. Miyashita, and N. Hagita. Proceedings of the 12th International Conference on Multimodal Interfaces and the 7th Workshop on Machine Learning for Multimodal Interfaces (IMCI-MLMI 2010), Beijing, China, page 19:1--19:8. (2010)