Submitted on: 07 April 2008.
Revised on: 28 April 2008.
Accepted on: 18 May 2008.
___________________BMC MUSCULOSKELETAL DISORDERS---BMC
http://reply.papertrans.cn/1/40/3908/3908-32.png
http://reply.papertrans.cn/1/40/3908/3908-33.png
Submitted on: 13 September 2010.
Revised on: 22 November 2010.
Accepted on: 20 December 2010.
___________________BMC MUSCULOSKELETAL DISORDERS---BMC
Submitted on: 12 November 2012.
Revised on: 03 March 2013.
Accepted on: 17 April 2013.
___________________BMC MUSCULOSKELETAL DISORDERS---BMC
http://reply.papertrans.cn/1/40/3908/3908-36.png