Submitted on: 04 January 2003.
Revised on: 19 March 2003.
Accepted on: 26 April 2003.
___________________ENVIRONMENT AND DEVELOPMENT ECONOMICS
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Submitted on: 10 May 1999.
Revised on: 09 July 1999.
Accepted on: 03 August 1999.
___________________ENVIRONMENT AND DEVELOPMENT ECONOMICS
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