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Submitted on: 13 April 2007.
Revised on: 02 July 2007.
Accepted on: 31 August 2007.
___________________Enfoque UTE---UNIV TECNOLOGICA EQUINOCCIAL
Submitted on: 09 January 2025.
Revised on: 02 May 2025.
Accepted on: 09 June 2025.
___________________Enfoque UTE---UNIV TECNOLOGICA EQUINOCCIAL
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Submitted on: 13 August 2011.
Revised on: 29 September 2011.
Accepted on: 12 November 2011.
___________________Enfoque UTE---UNIV TECNOLOGICA EQUINOCCIAL
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