RT Journal Article SR Electronic T1 Obstructive sleep apnoea: a progressive disorder? JF Thorax JO Thorax FD BMJ Publishing Group Ltd and British Thoracic Society SP 843 OP 844 DO 10.1136/thx.52.10.843 VO 52 IS 10 A1 P M Calverley YR 1997 UL http://thorax.bmj.com/content/52/10/843.abstract