Submitted on: 12 January 2006.
Revised on: 24 February 2006.
Accepted on: 09 March 2006.
___________________JMIR Public Health and Surveillance
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Submitted on: 15 November 2020.
Revised on: 12 March 2021.
Accepted on: 29 April 2021.
___________________JMIR Public Health and Surveillance
http://reply.papertrans.cn/2/150/14907/14907-24.png
http://reply.papertrans.cn/2/150/14907/14907-25.png
Submitted on: 17 October 2017.
Revised on: 02 February 2018.
Accepted on: 20 February 2018.
___________________JMIR Public Health and Surveillance
http://reply.papertrans.cn/2/150/14907/14907-27.png
Submitted on: 07 August 2014.
Revised on: 05 December 2014.
Accepted on: 20 January 2015.
___________________JMIR Public Health and Surveillance
http://reply.papertrans.cn/2/150/14907/14907-29.png
http://reply.papertrans.cn/2/150/14907/14907-30.png