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Submitted on: 10 February 1998.
Revised on: 26 April 1998.
Accepted on: 30 May 1998.
___________________CANADIAN MEDICAL ASSOCIATION JOURNAL
Submitted on: 02 May 1998.
Revised on: 08 June 1998.
Accepted on: 06 July 1998.
___________________CANADIAN MEDICAL ASSOCIATION JOURNAL
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