PT - JOURNAL ARTICLE AU - F Series TI - AUTHOR'S REPLY AID - 10.1136/thx.46.12.938-a DP - 1991 Dec 01 TA - Thorax PG - 938--938 VI - 46 IP - 12 4099 - http://thorax.bmj.com/content/46/12/938.2.short 4100 - http://thorax.bmj.com/content/46/12/938.2.full SO - Thorax1991 Dec 01; 46