Saleem, Shemaila, et al. “EFFECT OF HYPERTENSION AND SMOKING ON HEART RATE VARIABILITY IN PATIENTS WITH MYOCARDIAL INFARCTION”. Pakistan Journal of Physiology, vol. 8, no. 2, May 2018, pp. 24-27, https://pjp.pps.org.pk/index.php/PJP/article/view/785.