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. 2022 Mar 12;6(1):e100219. doi: 10.1136/bmjos-2021-100219

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© Author(s) (or their employer(s)) 2021. Re-use permitted under CC BY. Published by BMJ.

This is an open access article distributed in accordance with the Creative Commons Attribution 4.0 Unported (CC BY 4.0) license, which permits others to copy, redistribute, remix, transform and build upon this work for any purpose, provided the original work is properly cited, a link to the licence is given, and indication of whether changes were made. See: https://creativecommons.org/licenses/by/4.0/.

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Results of PubMed search performed on 3 March 2021 showing numbers of publications by year and totals for subject searches using ‘MeSH’ headings.