Submitted on: 17 November 2000.
Revised on: 21 December 2000.
Accepted on: 18 February 2001.
___________________BMC Chemistry---BMC
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Submitted on: 15 August 2004.
Revised on: 28 October 2004.
Accepted on: 10 November 2004.
___________________BMC Chemistry---BMC
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Submitted on: 24 April 2009.
Revised on: 02 June 2009.
Accepted on: 15 July 2009.
___________________BMC Chemistry---BMC
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Submitted on: 14 October 1999.
Revised on: 10 February 2000.
Accepted on: 11 March 2000.
___________________BMC Chemistry---BMC