http://reply.papertrans.cn/1/40/3949/3949-21.png
http://reply.papertrans.cn/1/40/3949/3949-22.png
http://reply.papertrans.cn/1/40/3949/3949-23.png
Submitted on: 17 August 2005.
Revised on: 25 October 2005.
Accepted on: 07 December 2005.
___________________BMJ Leader---BMJ PUBLISHING GROUP
http://reply.papertrans.cn/1/40/3949/3949-25.png
http://reply.papertrans.cn/1/40/3949/3949-26.png
Submitted on: 07 January 2018.
Revised on: 25 March 2018.
Accepted on: 27 April 2018.
___________________BMJ Leader---BMJ PUBLISHING GROUP
Submitted on: 13 September 2020.
Revised on: 22 November 2020.
Accepted on: 16 January 2021.
___________________BMJ Leader---BMJ PUBLISHING GROUP
http://reply.papertrans.cn/1/40/3949/3949-29.png
http://reply.papertrans.cn/1/40/3949/3949-30.png