1. http://www.goldcopd.org
2. http://www.who.int/healthinfo/paper36.pdf
3. http://www.who.int/healthinfo/global_burden_disease/GBD_report_2004update_full.pdf
4. Devine JF (2008) Chronic obstructive pulmonary disease: an overview. Am Health Drug Benefits 1(7): 34-42.
5. http://www.who.int/gard/publications/Risk%20factors.pdf