Submitted on: 13 January 2005.
Revised on: 02 February 2005.
Accepted on: 24 February 2005.
___________________CT&F-Ciencia Tecnologia y Futuro
Submitted on: 04 December 2002.
Revised on: 21 January 2003.
Accepted on: 04 February 2003.
___________________CT&F-Ciencia Tecnologia y Futuro
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Submitted on: 05 January 2003.
Revised on: 15 April 2003.
Accepted on: 12 May 2003.
___________________CT&F-Ciencia Tecnologia y Futuro
Submitted on: 09 March 2020.
Revised on: 29 March 2020.
Accepted on: 27 April 2020.
___________________CT&F-Ciencia Tecnologia y Futuro
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http://reply.papertrans.cn/1/68/6732/6732-17.png
Submitted on: 24 August 2000.
Revised on: 31 October 2000.
Accepted on: 28 December 2000.
___________________CT&F-Ciencia Tecnologia y Futuro
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Submitted on: 18 August 2019.
Revised on: 24 November 2019.
Accepted on: 14 December 2019.
___________________CT&F-Ciencia Tecnologia y Futuro