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. 2020 Dec 12;13(12):e236811. doi: 10.1136/bcr-2020-236811

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© BMJ Publishing Group Limited 2020. No commercial re-use. See rights and permissions. Published by BMJ.

This article is made freely available for use in accordance with BMJ’s website terms and conditions for the duration of the covid-19 pandemic or until otherwise determined by BMJ. You may use, download and print the article for any lawful, non-commercial purpose (including text and data mining) provided that all copyright notices and trade marks are retained.

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DOI: 10.1136/bcr-2020-236811.video06