Maryam Khan, and Naeem Aslam. “Prevalence of Caffeine Intake Among Cigarette Smokers: Directing Caffeine Use Disorder Among Pakistani Population”. Pakistan Journal of Medical Research, vol. 59, no. 1, July 2020, pp. 15-21, https://pjmr.org.pk/index.php/pjmr/article/view/60.