Markovics, Zigurds, Juris Lauznis, Matiss Erins, Olesja Minejeva, and Raivis Kivlenieks. 2018. “Testing and Analysis of the HRV Signals from Wearable Smart HRV Sensors”. International Journal of Engineering & Technology 7 (4.36): 1211-15. https://doi.org/10.14419/ijet.v7i4.36.28214.