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Submitted on: 03 September 2000.
Revised on: 18 December 2000.
Accepted on: 22 January 2001.
___________________BMC Primary Care---BMC
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http://reply.papertrans.cn/1/40/3924/3924-34.png
Submitted on: 12 May 2012.
Revised on: 31 July 2012.
Accepted on: 15 August 2012.
___________________BMC Primary Care---BMC
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