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Submitted on: 24 September 1998.
Revised on: 01 November 1998.
Accepted on: 27 November 1998.
___________________Forest Policy and Economics---ELSEVIER
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Submitted on: 13 April 2015.
Revised on: 18 June 2015.
Accepted on: 06 August 2015.
___________________Forest Policy and Economics---ELSEVIER
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