1. Allen, R. (1990). User models: Theory, method and practice. International Journal of Man-Machine Studies 32:511–543.
2. Broadbent, S., and Curran, S. (1992). The Assessment, Disability and Technology Handbook. Oldham: North West Regional ACCESS Centre and Oldham Education Department.
3. Brown, J., and Burton, R. (1978). Diagnostic models for procedural bugs in basic mathematical skills. Cognitive Science 2:155–192.
4. Casali, S. (1995). A physical skills based strategy for choosing an appropriate interface method. In Edwards, A. D. N., ed., Extra-Ordinary Human-Computer Interaction: Interfaces for Users with Disabilities. Cambridge University Press. chapter 17, 315–341.
5. Clancey, W. (1987). Knowledge-Based Tutoring: The GUIDON Program. MIT Press.