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2. World Health Organization. Rational use of personal protective equipment for coronavirus disease (COVID-19) and considerations during severe shortages: Interim guidance [Internet]. Geneva: World Health Organization; [2020 Apr 6; cited 2020 Apr 30]. Available from: https://www.who.int/publications-detail/rational-use-of-personal-protective-equipment-for-coronavirus-disease-(covid-19)-and-considerations-during-severe-shortages.
3. Chini M . Coronavirus: 3 million mouth masks don’t meet quality standards. The Brussels Times [Internet]. 2020 Apr 9 [cited 2020 Apr 30]. Available from: https://www.brusselstimes.com/all-news/belgium-all-news/105704/coronavirus-3-million-mouth-masks-dont-meet-quality-standards/.
4. National Institute for Occupational Safety and Health. Counterfeit Respirators / Misrepresentation of NIOSH-Approval [Internet]. Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health; [updated 2020 Apr 28; Cited 2020 Apr 30]. Available from: https://www.cdc.gov/niosh/npptl/usernotices/counterfeitResp.html.
5. European Committee for Standardization. EN 149:2009–08+AC:2019. _Respiratory protective devices - Filtering half masks to protect against particles - Requirements, testing, marking_. Brussels: CEN; 2009.