Submitted on: 16 June 2011.
Revised on: 26 July 2011.
Accepted on: 12 August 2011.
___________________ENDEAVOUR---PERGAMON-ELSEVIER SCIENCE LTD
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Submitted on: 02 February 2002.
Revised on: 30 March 2002.
Accepted on: 27 May 2002.
___________________ENDEAVOUR---PERGAMON-ELSEVIER SCIENCE LTD