RT Journal Article SR Electronic T1 Textbook of Respiratory Medicine, 2nd edition JF Occupational and Environmental Medicine JO Occup Environ Med FD BMJ Publishing Group Ltd SP 287 OP 287 DO 10.1136/oem.53.4.287 VO 53 IS 4 A1 Ayres, Jon YR 1996 UL http://oem.bmj.com/content/53/4/287.abstract AB