R. Bastide, D. Navarre, and P. Palanque. CHI '02 extended abstracts on Human factors in computing systems, page 516--517. Minneapolis, Minnesota, USA, ACM Press, (2002)
R. Popp, D. Montana, R. Gassner, G. Vidaver, and S. Iyer. IEEE International Conference on Systems, Man, and
Cybernetics, 3, page 2184--2189. San Diego, CA USA, IEEE, (11-14 October 1998)