1. Bock, G., Stebbins, L. B. and Proper, E. C. Education as experimentation: a planned variation model. Vol. IV B. Effects of follow through models. Report 76-196B. U.S. Office to Education, 1977.
2. Gajewski, S. An analysis of solution strategies and processing time in ratio and proportion problems. Unpublished M. A. Thesis, McGill University, 1980.
3. Lam, J. Finding the sum or addend in subtraction: a developmental classroom task. Unpublished paper OISE, 1979.
4. Stober, S. Teaching a specific type of vertical addition problem. Unpublished course assignment OISE, 1979.
5. Hammil, C. K. Teaching addition of one and two digit integers. Unpublished course assignment OISE, 1982.