Submitted on: 23 April 2009.
Revised on: 29 June 2009.
Accepted on: 30 July 2009.
___________________Green Materials---EMERALD GROUP PUBLISHING LTD
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Submitted on: 24 December 2008.
Revised on: 13 February 2009.
Accepted on: 09 March 2009.
___________________Green Materials---EMERALD GROUP PUBLISHING LTD
Submitted on: 03 November 2003.
Revised on: 18 February 2004.
Accepted on: 11 April 2004.
___________________Green Materials---EMERALD GROUP PUBLISHING LTD