Submitted on: 02 January 2007.
Revised on: 19 February 2007.
Accepted on: 05 April 2007.
___________________BULLETIN OF MATHEMATICAL BIOLOGY
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Submitted on: 15 March 2006.
Revised on: 30 June 2006.
Accepted on: 11 August 2006.
___________________BULLETIN OF MATHEMATICAL BIOLOGY
Submitted on: 16 January 2007.
Revised on: 15 February 2007.
Accepted on: 16 March 2007.
___________________BULLETIN OF MATHEMATICAL BIOLOGY
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Submitted on: 25 September 2001.
Revised on: 06 November 2001.
Accepted on: 05 December 2001.
___________________BULLETIN OF MATHEMATICAL BIOLOGY