http://reply.papertrans.cn/1/40/3928/3928-11.png
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http://reply.papertrans.cn/1/40/3928/3928-14.png
Submitted on: 09 March 2007.
Revised on: 15 April 2007.
Accepted on: 11 May 2007.
___________________BMC PUBLIC HEALTH---BMC
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Submitted on: 10 March 2024.
Revised on: 24 May 2024.
Accepted on: 21 July 2024.
___________________BMC PUBLIC HEALTH---BMC