Submitted on: 24 January 2001.
Revised on: 18 February 2001.
Accepted on: 01 March 2001.
___________________GEM-International Journal on Geomathematics
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Submitted on: 21 October 2021.
Revised on: 31 December 2021.
Accepted on: 31 January 2022.
___________________GEM-International Journal on Geomathematics
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Submitted on: 07 February 2020.
Revised on: 21 March 2020.
Accepted on: 25 April 2020.
___________________GEM-International Journal on Geomathematics
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