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. 2018 Apr 25;2018(4):CD011526. doi: 10.1002/14651858.CD011526.pub2

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Copyright © 2018 The Authors. Cochrane Database of Systematic Reviews published by John Wiley & Sons, Ltd. on behalf of The Cochrane Collaboration.

This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial License, which allows remixing, tweaking, and building upon the original work non-commercially, and although the new works must also acknowledge the original work and be non-commercial, derivative works don’t have to be licensed under the same terms.

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‘Risk of bias' summary: review authors' judgements about each risk of bias item for each included study.