Corbett, A. T., Anderson, J. R., & Patterson, E. G., (1990). Student modelling and tutoring flexibility in the LISP Intelligent Tutoring System. In C. Frasson and G. Gauthier (Eds.) Intelligent tutoring systems: At the crossroads of artificial intelligence and education. 83-106. Norwood, NJ: Ablex. [] [info]

Corbett, A. T., Anderson, J. R., & Patterson, E. J. (1988). Problem compilation and tutoring flexibility in the LISP Tutor. Intelligent Tutoring Systems, 423-429. [] [info]