Trawka, Paulina, Michał Wilczyński, Mateusz Porada, Agnieszka Nawrocka, Ewelina Flegiel, Paweł Mlicki, Olga Rymarska, et al. 2019. “The Impact of Influenza on Elderly Patients”. Journal of Education, Health and Sport 9 (7):303-12. https://apcz.umk.pl/JEHS/article/view/7146.