ZIELIŃSKA-SITKIEWICZ, M. THE FLU: AN ANALYSIS OF ECONOMIC COSTS AND MORBIDITY RATES IN POLAND IN THE PERIOD 2013–2019 USING ADAPTIVE PREDICTION METHODS. Acta Scientiarum Polonorum. Oeconomia, v. 19, n. 4, p. 139-146, 3 Jan. 2021.