1. Centre d'Études de la, Navigation Aérienne, 7 avenue Edouard Belin, 31055 Toulouse cedex, France and Input Research Group, CSRI, University of Toronto, Toronto, ON M5S 1A4, Canada
2. Input Research Group, CSRI, University of Toronto, Toronto, ON M5S 1A4, Canada and IBM Almaden, Research Center, 650 Harry Road, San Jose, CA