1. Exposure to second hand smoke at home and work among nonsmokers
2. National Health Statistics for 2015 (National Health Effects Survey, Phase 6, Third Year Data), Disease Control Headquarters. https://knhanes.cdc.go.kr/knhanes/sub01/sub01_05.jsp#s5_01_01. Accessed 15 Aug 2018
3. OECD Data; Health at a glance (2017). https://data.oecd.org/healthrisk/daily-smokers.htm. Accessed 15 Aug 2018
4. National Health Promotion Act, Article 9 (Date 31, Dec, 2011). https://elaw.klri.re.kr/eng_service/lawView.do?hseq=43278&lang=ENG
5. Smoke-free laws and secondhand smoke exposure in US non-smoking adults, 1999-2002