S. Yoon, J. Yun, S. Kim, and J. Kim. Agent Mediated Electronic Commerce (IJCAI Workshop), volume 1788 of Lecture Notes in Computer Science, page 102-112. Springer, (1999)
L. Fais, K. ho Loken-Kim, and Y. Park. Multimodal Human-Computer Communication, volume 1374 of Lecture Notes in Computer Science, page 264-278. Springer, (1995)