Submitted on: 19 June 2006.
Revised on: 27 July 2006.
Accepted on: 11 September 2006.
___________________Economics and Business Letters
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Submitted on: 18 May 1998.
Revised on: 23 July 1998.
Accepted on: 18 August 1998.
___________________Economics and Business Letters
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Submitted on: 26 July 2014.
Revised on: 30 September 2014.
Accepted on: 15 November 2014.
___________________Economics and Business Letters
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