Submitted on: 16 January 2002.
Revised on: 03 May 2002.
Accepted on: 29 June 2002.
___________________IEEE Transactions on Learning Technologies
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Submitted on: 28 February 2007.
Revised on: 27 May 2007.
Accepted on: 04 July 2007.
___________________IEEE Transactions on Learning Technologies
Submitted on: 29 September 2004.
Revised on: 28 November 2004.
Accepted on: 26 January 2005.
___________________IEEE Transactions on Learning Technologies
Submitted on: 02 April 2004.
Revised on: 21 June 2004.
Accepted on: 17 August 2004.
___________________IEEE Transactions on Learning Technologies
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