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Submitted on: 13 February 2002.
Revised on: 10 March 2002.
Accepted on: 01 April 2002.
___________________Discover Sustainability---SPRINGERNATURE
Submitted on: 09 October 2001.
Revised on: 02 January 2002.
Accepted on: 01 February 2002.
___________________Discover Sustainability---SPRINGERNATURE