Trifonova, Iva, Svetla Angelova, and Neli Korsun. “AETIOLOGICAL STRUCTURE OF ACUTE RESPIRATORY TRACT INFECTIONS AMONG CHILDREN YOUNGER THAN 5 YEARS IN BULGARIA”. PROBLEMS of Infectious and Parasitic Diseases 47, no. 1 (June 27, 2019): 9–15. Accessed December 13, 2024. https://pipd.ncipd.org/index.php/pipd/article/view/47_1_2_AETIOLOGICAL_STRUCTURE_OF_ACUTE_RESPIRATORY_TRACT_INFECTI.