Still Confused About Masks? Here’s the Science Behind How Face Masks Prevent Coronavirus..
University of California San Francisco (UCSF) Special Notice Concerning Covid-19, June 26th 2020
https://www.ucsf.edu/news/2020/06/417906/still-confused-about-masks-heres-science-behind-how-face-masks-prevent accessed July 11th 2020
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