Submitted on: 26 November 2002.
Revised on: 01 January 2003.
Accepted on: 14 January 2003.
Latvian Journal of Physics and Technical Sciences
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Submitted on: 09 October 2010.
Revised on: 28 October 2010.
Accepted on: 02 November 2010.
Latvian Journal of Physics and Technical Sciences
Submitted on: 14 January 2016.
Revised on: 19 February 2016.
Accepted on: 09 March 2016.
Latvian Journal of Physics and Technical Sciences
Submitted on: 15 March 2001.
Revised on: 19 April 2001.
Accepted on: 13 May 2001.
Latvian Journal of Physics and Technical Sciences
Submitted on: 07 January 2015.
Revised on: 30 January 2015.
Accepted on: 14 February 2015.
Latvian Journal of Physics and Technical Sciences
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