1. World health organization fact sheets. Fact sheet N°297 Reviewed January 2013. Available from: http: //www.who.int/mediacentre/factsheets/fs297/en/.
2. Global initiative for chronic obstructive lung disease, 2013. Global strategy for the diagnosis, management and prevention of COPD, global initiative for chronic obstructive lung disease (GOLD). .
3. Interpreting COPD Prevalence Estimates
4. Global burden of COPD: systematic review and meta-analysis
5. Projections of Global Mortality and Burden of Disease from 2002 to 2030