Ababulgu, Sabit Abazinab, Nebiyu Dereje, and Abiot Girma. “Secondhand Tobacco Smoke Exposure Among Adolescents in an Ethiopian School”. Healthcare in Low-resource Settings 4, no. 1 (May 30, 2016). Accessed June 24, 2019. https://www.pagepressjournals.org/index.php/hls/article/view/5584.