Yordanova, Violeta, Slaveija Dimitrova, Magdalena Marinova, Diana Valcheva, Viktor Kirchev, and Todor Tcherkezov. “Retrospective Analysis of COVID 2020 Epidemiological Data in the Town of Kardzhali”. International Journal of Medical Science and Clinical Invention 9, no. 01 (January 16, 2022): 5924–5930. Accessed November 24, 2024. http://valleyinternational.net/index.php/ijmsci/article/view/3345.