Ilić, Miroslav, Ivan Kopitović, Aleksandra Vulin, Biljana Zvezdin, Sanja Hromiš, Violeta Kolarov, Danijela Kuhajda, and Marija Vukoja. 2021. “Frequency and Effects of Seasonal Flu Vaccines on Exacerbations of Chronic Obstructive Pulmonary Disease in Serbia”. Vojnosanitetski Pregled 78 (2). https://doi.org/10.2298/VSP181214049I.