Lavelin, S., S. Panchuk, and O. Gololobova. “HEART RATE VARIABILITY INDICES IN PATIENTS WITH VIRAL HEPATITIS”. The Journal of V. N. Karazin Kharkiv National University, Series "Medicine", no. 6, 1, pp. 52-55, https://periodicals.karazin.ua/medicine/article/view/7298.