Risdiana, N., S. Syahruramdhani, and A. Suwitno. “The Physical Fitness Level, Heart Rate, and Heart Rate Recovery Among Adolescent Smokers and Non-Smokers”. Open Access Macedonian Journal of Medical Sciences, vol. 9, no. T4, Mar. 2021, pp. 101-5, doi:10.3889/oamjms.2021.5805.