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. 2017 Feb 8;1:3. doi: 10.1186/s41512-016-0005-7

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© The Author(s) 2017

Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

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Fig. 2 — Risk of bias assessment summary. Risk of bias assessment for six predefined domains for each included study. Legend: green, low risk of bias; yellow, medium risk of bias; red, high risk of bias