S. Watanabe, J. Hershey, Y. Marks, Tim K. Fujii, and Y. Koji. Proceedings of INTERSPEECH 2014, 15th Annual Conference of the International Speech Communication Association, Singapore, page 323-327. (2014)
J. Mackinlay, R. Rao, and S. Card. Proceedings of the SIGCHI Conference on Human Factors in Computing Systems, page 67--73. New York, NY, USA, ACM Press/Addison-Wesley Publishing Co., (1995)