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Submitted on: 04 February 2015.
Revised on: 29 May 2015.
Accepted on: 01 July 2015.
___________________BMC Primary Care---BMC
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Submitted on: 25 June 1999.
Revised on: 18 October 1999.
Accepted on: 11 November 1999.
___________________BMC Primary Care---BMC
http://reply.papertrans.cn/1/40/3924/3924-29.png
Submitted on: 07 July 1998.
Revised on: 09 August 1998.
Accepted on: 02 September 1998.
___________________BMC Primary Care---BMC