. 2017 Jul 31;12:2239–2256. doi: 10.2147/COPD.S137868
© 2017 Smith et al. This work is published by Dove Medical Press Limited, and licensed under a Creative Commons Attribution License
The full terms of the License are available at http://creativecommons.org/licenses/by/4.0/. The license permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.