RT Journal Article SR Electronic T1 Proceedings of the Thoracic Society JF Thorax JO Thorax FD BMJ Publishing Group Ltd and British Thoracic Society SP 478 OP 482 DO 10.1136/thx.22.5.478 VO 22 IS 5 YR 1967 UL http://thorax.bmj.com/content/22/5/478.abstract AB