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Start with what someone already synthesized

Before building a search string, we check whether someone has already synthesized the evidence: the Cochrane Library for healthcare interventions, the Campbell Collaboration for social interventions, WHO guidelines. A relevant review hands us a curated bibliography, and Google Scholar's Cited by feature finds what has appeared since. Scholar indexes broadly for early exploration, including grey literature, but it hides what it searches, uses no controlled vocabulary, and returns predatory journals, so it discovers rather than proves. Stop when searches keep returning papers already seen.

Also covered: randomized controlled trials · evidence pyramid · exploratory searching · related articles feature