Submitted on: 10 August 2007.
Revised on: 26 August 2007.
Accepted on: 04 September 2007.
Romanian Journal of Physics---EDITURA ACAD ROMANE
http://reply.papertrans.cn/3/274/27326/27326-12.png
Submitted on: 25 July 2012.
Revised on: 23 August 2012.
Accepted on: 05 September 2012.
Romanian Journal of Physics---EDITURA ACAD ROMANE
http://reply.papertrans.cn/3/274/27326/27326-14.png
Submitted on: 21 October 2005.
Revised on: 05 November 2005.
Accepted on: 27 November 2005.
Romanian Journal of Physics
http://reply.papertrans.cn/3/274/27326/27326-16.png
Submitted on: 07 September 2004.
Revised on: 09 October 2004.
Accepted on: 29 October 2004.
Romanian Journal of Physics
http://reply.papertrans.cn/3/274/27326/27326-18.png
Submitted on: 31 August 2011.
Revised on: 17 September 2011.
Accepted on: 04 October 2011.
Romanian Journal of Physics---EDITURA ACAD ROMANE
Submitted on: 28 August 2010.
Revised on: 29 September 2010.
Accepted on: 12 October 2010.
Romanian Journal of Physics