A Formative Evaluation of the PACT Algebra II Tutor: Support for Simple Hierarchical Reasoning. - Albert T. Corbett; Holly J. Trask; K. Christine Scarpinatto; William S. Hadley (Intelligent Tutoring Systems, 1998)

Instructional interventions in computer-based tutoring: differential impact on learning time and accuracy. - Albert T. Corbett; Holly J. Trask (CHI, 2000)