Submitted on: 31 August 2004.
Revised on: 03 October 2004.
Accepted on: 23 October 2004.
Romanian Journal of Physics---EDITURA ACAD ROMANE
Submitted on: 14 May 2004.
Revised on: 07 June 2004.
Accepted on: 22 June 2004.
Romanian Journal of Physics---EDITURA ACAD ROMANE
Submitted on: 16 December 2003.
Revised on: 12 January 2004.
Accepted on: 30 January 2004.
Romanian Journal of Physics
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Submitted on: 03 March 2008.
Revised on: 29 March 2008.
Accepted on: 18 April 2008.
Romanian Journal of Physics
Submitted on: 23 July 2003.
Revised on: 06 August 2003.
Accepted on: 29 August 2003.
Romanian Journal of Physics
http://reply.papertrans.cn/3/274/27326/27326-27.png
Submitted on: 26 March 2002.
Revised on: 09 May 2002.
Accepted on: 23 May 2002.
Romanian Journal of Physics
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