Submitted on: 15 September 2003.
Revised on: 17 November 2003.
Accepted on: 17 December 2003.
___________________Journal of Spatial Science---TAYLOR & FRANCIS LTD
Submitted on: 06 January 2008.
Revised on: 14 February 2008.
Accepted on: 02 April 2008.
___________________Journal of Spatial Science---TAYLOR & FRANCIS LTD
Submitted on: 18 February 2006.
Revised on: 05 April 2006.
Accepted on: 18 May 2006.
___________________Journal of Spatial Science---TAYLOR & FRANCIS LTD
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