Shanina, I. V., and D. E. Volkov. “PACING PARAMETERS CHANGES IN PATIENTS WITH IMPLANTED PACEMAKER IN DIFFERENT QRS COMPLEX DURATION CLASSES AT THE ANNUAL OBSERVATION STAGE”. The Journal of V. N. Karazin Kharkiv National University, Series "Medicine", no. 29, Aug. 2015, pp. 49-52, https://periodicals.karazin.ua/medicine/article/view/3755.