Kolomytseva, I. M., D. E. Volkov, D. A. Lopin, and M. I. Yabluchansky. “FUNCTIONAL CLASS OF CHRONIC HEART FAILURE AND CLINICAL FEATURES OF PATIENTS WITH PERMANENT PACEMAKERS”. The Journal of V. N. Karazin Kharkiv National University, Series "Medicine", no. 27, July 2015, pp. 5-9, https://periodicals.karazin.ua/medicine/article/view/3424.