Submitted on: 26 April 1998.
Revised on: 08 June 1998.
Accepted on: 15 July 1998.
___________________BMJ Evidence-Based Medicine---BMJ PUBLISHING GROUP
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Submitted on: 03 March 2015.
Revised on: 16 April 2015.
Accepted on: 12 June 2015.
___________________BMJ Evidence-Based Medicine---BMJ PUBLISHING GROUP
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Submitted on: 10 March 2001.
Revised on: 06 April 2001.
Accepted on: 30 April 2001.
___________________BMJ Evidence-Based Medicine---BMJ PUBLISHING GROUP
Submitted on: 21 October 2010.
Revised on: 23 November 2010.
Accepted on: 06 December 2010.
___________________BMJ Evidence-Based Medicine---BMJ PUBLISHING GROUP
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