Z. Fei, J. Liu, and G. Wu. Proceedings of the 4th International Conference on Computer and Information
Technology (CIT-2004), page 1147--1152. Wuhan, China, (2004)
H. Liu, H. Lieberman, and T. Selker. Proceedings of the International Conference on Intelligent User Interfaces
(IUI-2003), page 125-132. Miami, Florida, (2003)