Submitted on: 03 May 2006.
Revised on: 25 May 2006.
Accepted on: 29 June 2006.
___________________ANNALS OF REGIONAL SCIENCE---SPRINGER
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Submitted on: 29 June 2012.
Revised on: 14 October 2012.
Accepted on: 26 October 2012.
___________________ANNALS OF REGIONAL SCIENCE---SPRINGER
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Submitted on: 05 August 2015.
Revised on: 29 September 2015.
Accepted on: 27 October 2015.
___________________ANNALS OF REGIONAL SCIENCE---SPRINGER
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