| Http://: http://www.niehs.nih.gov/health/topics/conditions/lung-disease/index.cfm |
| Http://: http://www.nlm.nih.gov/medlineplus/ency/article/000066.htm |
| Http://: http://www.niehs.nih.gov/health/topics/conditions/lung-disease/index.cfm |
| Http://: http://www.nlm.nih.gov/medlineplus/ency/article/000066.htm |