- Dr C F Ryan, Division of Respiratory Medicine, Vancouver General Hospital, 2775 Heather Street, Vancouver, British Columbia, V5Z 3J5 Canada email:
- Received 22 November 1999
- Revision requested 12 January 2000
- Revised 8 February 2000
- Accepted 8 February 2000
- Published online 1 May 2000.
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