An official website of the United States government
The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before
sharing sensitive information, make sure you’re on a federal
government site.
The site is secure.
The https:// ensures that you are connecting to the
official website and that any information you provide is encrypted
and transmitted securely.
O'Driscoll BR, Howard LS, Davison AG; British Thoracic Society.O'Driscoll BR, et al.Clin Med (Lond). 2011 Aug;11(4):372-5. doi: 10.7861/clinmedicine.11-4-372.Clin Med (Lond). 2011.PMID: 21853838Free PMC article.
Harris A, O'Driscoll BR, Turkington PM.Harris A, et al.Postgrad Med J. 2010 Feb;86(1012):68-72. doi: 10.1136/pgmj.2009.087759.Postgrad Med J. 2010.PMID: 20145053