Submitted on: 24 November 2007.
Revised on: 07 January 2008.
Accepted on: 21 January 2008.
___________________EUROPEAN JOURNAL OF PHYSICS---IOP PUBLISHING LTD
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Submitted on: 28 September 2010.
Revised on: 05 January 2011.
Accepted on: 03 February 2011.
___________________EUROPEAN JOURNAL OF PHYSICS---IOP PUBLISHING LTD
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Submitted on: 06 September 2010.
Revised on: 17 December 2010.
Accepted on: 28 January 2011.
___________________EUROPEAN JOURNAL OF PHYSICS---IOP PUBLISHING LTD
Submitted on: 08 February 2024.
Revised on: 20 March 2024.
Accepted on: 26 April 2024.
___________________EUROPEAN JOURNAL OF PHYSICS---IOP PUBLISHING LTD
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