Taan Al. Awar, D. H., A. H. Al Yafei, and A. A. S. Al Fehaidi. “Smoking and Its Effects on Heart Rate Variability”. International Journal of Research in Medical Sciences, vol. 10, no. 4, Mar. 2022, pp. 933-6, doi:10.18203/2320-6012.ijrms20220988.