Pagaduan, J., E. Užičanin, M. Muratović, and H. Pojskić. “Accuracy and Reliability of a Free Mobile HRV Application in Measurement of Heart Rate Variability”. Journal of Human Sport and Exercise, vol. 14, no. 4proc, Oct. 2019, pp. S578-S583, doi:10.14198/jhse.2019.14.Proc4.15.