- Educational Technology & Society 8(1):17--27 (2005)
- proceedings of the Annual Meeting of the 26th Annual Meeting of the International Group for the Psychology of Mathematics Education PME, 2, page 273-280. Norwich, UK, University of Norwich, (July 2002)
- Educational Psychology Review (1989)
- IEEE Computer 18(9):8-19 (1985)
- the 24th Conference of the International Group for the Psychology of Mathematics Education PME, 1, page 23--38. Hiroshima, Japan, (2000)
- Distance Education 27(2):171--185 (2006)
- International Journal of Human-Computer Studies (2002)
- Journal of Computer Assisted Learning 7(4):210--228 (1991)


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