Kassem @kassem CC BY-NC-SA 4/12/2020 3 3 Face masks considerably reduce #COVID-19 cases in Germany | PNAS▻https://www.pnas.org/content/early/2020/12/02/2015954117 https://www.pnas.org/content/early/2020/12/02/2015954117/F1.large.jpg #masques #Allemagne Kassem @kassem CC BY-NC-SA