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. 2021 May 7;9(5):23259671211002282. doi: 10.1177/23259671211002282

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© The Author(s) 2021

This article is distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 License (https://creativecommons.org/licenses/by-nc-nd/4.0/) which permits non-commercial use, reproduction and distribution of the work as published without adaptation or alteration, without further permission provided the original work is attributed as specified on the SAGE and Open Access pages (https://us.sagepub.com/en-us/nam/open-access-at-sage).

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Figure 3. — Quality assessment of the included studies. (A) Graph of the risk of different types of bias. (B) Summary of bias risk. + = low risk of bias; − = high risk of bias; ? = unclear or unknown risk of bias.