Submitted on: 20 June 2009.
Revised on: 04 August 2009.
Accepted on: 20 September 2009.
___________________European Physical Journal Plus
Submitted on: 27 November 2019.
Revised on: 15 February 2020.
Accepted on: 24 March 2020.
___________________European Physical Journal Plus
Submitted on: 01 October 2017.
Revised on: 18 January 2018.
Accepted on: 22 February 2018.
___________________European Physical Journal Plus
Submitted on: 07 May 2021.
Revised on: 02 September 2021.
Accepted on: 03 October 2021.
___________________European Physical Journal Plus
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Submitted on: 16 February 2000.
Revised on: 04 April 2000.
Accepted on: 11 May 2000.
___________________European Physical Journal Plus
Submitted on: 21 December 2011.
Revised on: 16 March 2012.
Accepted on: 09 May 2012.
___________________European Physical Journal Plus
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