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Submitted on: 18 October 1998.
Revised on: 10 February 1999.
Accepted on: 28 February 1999.
___________________Education and Information Technologies
Submitted on: 26 November 2005.
Revised on: 10 January 2006.
Accepted on: 09 February 2006.
___________________Education and Information Technologies
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Submitted on: 31 May 2017.
Revised on: 02 July 2017.
Accepted on: 26 August 2017.
___________________Education and Information Technologies