Submitted on: 23 February 2000.
Revised on: 26 April 2000.
Accepted on: 18 June 2000.
___________________ETR&D-EDUCATIONAL TECHNOLOGY RESEARCH AND DEVELOPMENT
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Submitted on: 29 March 2005.
Revised on: 20 July 2005.
Accepted on: 12 September 2005.
___________________ETR&D-EDUCATIONAL TECHNOLOGY RESEARCH AND DEVELOPMENT
Submitted on: 22 September 2015.
Revised on: 20 January 2016.
Accepted on: 14 March 2016.
___________________ETR&D-EDUCATIONAL TECHNOLOGY RESEARCH AND DEVELOPMENT