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. 2017 Feb 23;7(2):e012680. doi: 10.1136/bmjopen-2016-012680

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PRISMA diagram of included studies. *McRobbie, 2014.⁸ **Further two publications from one RCT included by the Cochrane review were identified only in our search strategy. ***Further one publication from one cohort study identified by our search strategy was identified throughout the expert search.