RT Journal Article SR Electronic T1 Universal masking for COVID-19: evidence, ethics and recommendations JF BMJ Global Health JO BMJ Global Health FD BMJ Publishing Group Ltd SP e002819 DO 10.1136/bmjgh-2020-002819 VO 5 IS 5 A1 Chan, Tak Kwong YR 2020 UL http://gh.bmj.com/content/5/5/e002819.abstract AB