Submitted on: 25 June 2012.
Revised on: 09 October 2012.
Accepted on: 01 November 2012.
___________________International Journal of Biomathematics
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Submitted on: 21 August 2004.
Revised on: 12 December 2004.
Accepted on: 29 January 2005.
___________________International Journal of Biomathematics
http://reply.papertrans.cn/2/131/13088/13088-34.png
Submitted on: 08 August 2000.
Revised on: 05 October 2000.
Accepted on: 07 November 2000.
___________________International Journal of Biomathematics
Submitted on: 02 November 2004.
Revised on: 11 January 2005.
Accepted on: 29 January 2005.
___________________International Journal of Biomathematics