Submitted on: 02 March 2007.
Revised on: 27 April 2007.
Accepted on: 18 June 2007.
___________________Econometrics and Statistics---ELSEVIER
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Submitted on: 16 June 2018.
Revised on: 02 August 2018.
Accepted on: 15 September 2018.
___________________Econometrics and Statistics---ELSEVIER
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Submitted on: 17 April 2012.
Revised on: 04 July 2012.
Accepted on: 24 August 2012.
___________________Econometrics and Statistics---ELSEVIER
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