S. Shaw, and J. Hudson. E-Learn 2004: World Conference on E-Learning in Corporate, Government, Healthcare & Higher Education, page 1694--1698. Chesapeake, VA, Association for the Advancement of Computing in Education (AACE), AACE, (2004)
S. Schluep, P. Ravasio, and S. Schär. Proceedings of Human-Computer Interact -- INTERACT'03, page 884-887. Zurich, Switzerland, IFIP TC13, IOS Press, (September 2003)