1. (2022, September 14). Available online: https://www.philips.com/aw/about/news/archive/standard/news/press/2021/20210310-philipssurvey-reveals-covid-19-s-negative-impact-on-sleep-quality-and-cpapuse.html.
2. (2022, September 14). Available online: https://kokodoc.com/sleep-health-03/.
3. (2022, September 14). Available online: http://www.sleepmed.or.kr/content/info/sleeptime.html.
4. Optical Wrist-Worn Device for Sleep Monitoring;Eskola;EMBEC NBC 2017,2017
5. (2022, September 14). 2004 After Rechtschaffen & Kale, 1968, Kalat, 2005, Weiten. Available online: https://www.basicknowledge101.com/subjects/sleeping.html.