Submitted on: 16 February 2007.
Revised on: 12 April 2007.
Accepted on: 10 May 2007.
___________________BMC Pulmonary Medicine---BMC
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Submitted on: 03 November 2017.
Revised on: 14 January 2018.
Accepted on: 18 February 2018.
___________________BMC Pulmonary Medicine---BMC
Submitted on: 14 April 1999.
Revised on: 21 June 1999.
Accepted on: 09 August 1999.
___________________BMC Pulmonary Medicine---BMC
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Submitted on: 06 November 2002.
Revised on: 28 January 2003.
Accepted on: 18 March 2003.
___________________BMC Pulmonary Medicine---BMC