Fritzsche, L., M. Fritzsche, and D. Majoe. “Optimi (Online Predicative Tools For Intervention In Mental Illness). Biofeedback Based On Heart Rate Variability As A Preventive Tool Against Stress-Related Disorders”. Psychiatry, Neurology and Medical Psychology, Vol. 2, no. 2 (4), Aug. 2016, pp. 48–52, https://periodicals.karazin.ua/pnmp/article/view/6231.