Hameed, S., A. Almas, F. S. Ahmed, and A. H. Khan. “Descriptive Controlled Study Regarding the Effects of Negative Chronotropic Agents on Lowering Heart Rate and Morning Surge in a Tertiary Care Hospital ”. National Journal of Health Sciences, vol. 1, no. 1, Jan. 2021, pp. 25-29, https://ojs.njhsciences.com/index.php/njhs/article/view/153.