1. Ainsworth, S. (1997). Designing and evaluating multi-representational learning environments for primary mathematics. PhD thesis. Technical Report 47, Centre for Research in Development, Instruction & Training, University of Nottingham.
2. Visual discovery in mind and on paper;Anderson;Memory and Cognition,1993
3. Baddeley, A. D. (1990). Human memory: Theory and practice. Hillsdale, NJ: Lawrence Erlbaum & Associates.
4. Barwise, J., & Etchemendy, J. (1994). Hyperproof for the Macintosh. CSLI Lecture Notes Number 42, Centre for the Study of Language & Information, Leland Stanford Junior University: CSLI Publications.
5. Bryant, D. J. (1992). A spatial representation system in humans. Psycoloquy (electronic journal sponsored by American Psychological Association), Internet, May.