- Dr J M Liebler, Pulmonary and Critical Care Medicine Division, Oregon Health Sciences University UHN-67, 3181 S W Sam Jackson Park Road, Portland, Oregon 97201–3098, USA.
- Received 24 September 1997
- Revision requested 11 December 1997
- Revised 25 March 1998
- Accepted 26 May 1998
- Published online 1 October 1998.
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