Akhter, Q. F., Q. S. Akhter, F. Rahman, S. Ferdousi, and S. Sinha. “Power Spectral Analysis of Heart Rate Variability in Bangladeshi Healthy Population of Different Age”. Bangladesh Journal of Physiology and Pharmacology, vol. 30, no. 1, Nov. 2014, pp. 11-15, doi:10.3329/bjpp.v30i1.20788.