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Submitted on: 21 November 1999.
Revised on: 01 January 2000.
Accepted on: 17 February 2000.
___________________Forest Policy and Economics---ELSEVIER
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Submitted on: 14 October 2010.
Revised on: 20 January 2011.
Accepted on: 26 February 2011.
___________________Forest Policy and Economics---ELSEVIER
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