Pambudi, Gigih Cita, Setyo Sri Rahardjo, and Sumardiyono Sumardiyono. 2021. “A Meta-Analysis of Correlations Between Chronic Obstructive Pulmonary Disease, Smoking, and Severity of COVID-19”. Journal of Epidemiology and Public Health 6 (4):415-25. https://www.jepublichealth.com/index.php/jepublichealth/article/view/437.