Int. J. Environ. Res. Public Health 2009, 6 224 96. Pride, N.B. Smoking cessation: effects on symptoms, spirometry and future trends in COPD. Thorax 2001, 56, ii7-ii10. © 2009 by the authors; licensee Molecular Diversity Preservation International, Basel, Switzerland. This article is an open-access article distributed under the terms and conditions of the Creative Commons Attribution license (http://creativecommons.org/licenses/by/3.0/).