1. Global Initiative for Chronic Obstructive Lung Disease. Global strategy for the diagnosis, management, and prevention of chronic obstructive pulmonary disease. 2021 report; Accessed from: https://goldcopd.org/wp-content/uploads/2020/11/GOLD-REPORT-2021-v1.1-25Nov20_WMV.pdf; 2021 Accessed at: April 5, 2021]
2. The long-term burden of COPD exacerbations during maintenance therapy and lung function decline;Kerkhof;Int J Chron Obstruct Pulmon Dis,2020
3. COPD exacerbations: defining their cause and prevention;Wedzicha;Lancet,2007
4. Relation of sputum inflammatory markers to symptoms and lung function changes in COPD exacerbations;Bhowmik;Thorax,2000
5. Relationship between exacerbation frequency and lung function decline in chronic obstructive pulmonary disease;Donaldson;Thorax,2002