RT Journal Article SR Electronic T1 Tracheal Extension in Respiration JF Thorax JO Thorax FD BMJ Publishing Group Ltd and British Thoracic Society SP 201 OP 210 DO 10.1136/thx.14.3.201 VO 14 IS 3 A1 R. S. Harris YR 1959 UL http://thorax.bmj.com/content/14/3/201.abstract AB