Submitted on: 05 February 1999.
Revised on: 03 April 1999.
Accepted on: 15 April 1999.
___________________JOURNAL OF EDUCATIONAL COMPUTING RESEARCH
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Submitted on: 22 April 2002.
Revised on: 21 June 2002.
Accepted on: 12 August 2002.
___________________JOURNAL OF EDUCATIONAL COMPUTING RESEARCH
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Submitted on: 14 July 2003.
Revised on: 18 August 2003.
Accepted on: 10 September 2003.
___________________JOURNAL OF EDUCATIONAL COMPUTING RESEARCH
Submitted on: 06 December 2009.
Revised on: 16 March 2010.
Accepted on: 07 April 2010.
___________________JOURNAL OF EDUCATIONAL COMPUTING RESEARCH