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. 2015 Dec 30;4:835. doi: 10.1186/s40064-015-1604-4

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© Hadi et al. 2015

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.

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Fig. 2 — PRISMA flow diagram including the details of our search results for this review. Figure shows the reasons behind study exclusion at each stage of the search and the number of studies identified at each point of the search