A major review can give you a strong starting point, but its publication date does not tell you where its evidence ends. Find its last search date, understand how it searched, then systematically retrieve the research that appeared afterward.
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Database alerts rerun a saved search against newly added records and notify you when something matches. The useful ones come from searches precise enough to catch important new research without flooding you with irrelevant results.
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Sometimes the most recent evidence is available only as a preprint or another research output that has not completed peer review. You do not necessarily need to ignore it, but its preliminary status should affect how you evaluate, describe, cite, and rely on it.
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Grey literature includes research and other evidence produced outside conventional academic and commercial publishing. Learn what counts as grey literature and when searching for it can materially improve a literature review.
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Ignoring grey literature can leave a review with a systematically incomplete evidence base, especially when the availability of research depends on its results. The problem is not simply missing studies, but whether the evidence you can find differs from the evidence you cannot.
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Theses, dissertations, reports, and working papers are scattered across repositories, specialist databases, organizational websites, and search engines. Learn where to search and how to find documents that conventional journal databases may miss.
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A conference abstract with no identifiable full paper should not simply disappear from your review. Trace the study carefully, seek additional information where appropriate, and decide what the abstract can support based on your review criteria and the information actually available.
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Government and institutional reports can contain valuable research evidence, including surveys, evaluations, administrative analyses, and technical studies. Their authority as documents, however, should not be confused with the methodological strength of the evidence they contain.
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A report does not become unreliable simply because it was never peer reviewed, but you cannot assume that someone else has checked it for you. Evaluate its provenance, methods, data, transparency, potential bias, and the strength of the claims it actually supports.
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When a preprint has subsequently become a peer-reviewed journal article, the journal version will usually be the appropriate source to cite. But the preprint should not automatically disappear when it contains unique information or differs meaningfully from the published paper.
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When a preprint and its published paper report different results, do not automatically discard one version or assume peer review explains the change. Compare the study versions systematically to determine what changed, why it matters, and which result should inform your interpretation.
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Studies can exist long before, or without ever becoming, journal articles. Learn how to trace unpublished and ongoing research through registries, conference records, repositories, study authors, sponsors, and other sources.
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Publication bias occurs when whether research becomes publicly available is influenced by its findings. The result can be a published literature that looks more positive, consistent, or convincing than the underlying body of research actually is.
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The file drawer problem occurs when completed research, particularly studies with null, non-significant, or otherwise unremarkable findings, remains undisclosed. When those hidden studies differ systematically from published research, the visible literature can give a misleading impression of the evidence.
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Searching for unpublished research can reduce the risk of missing important evidence, but it can also require substantial time for uncertain return. The right level of effort depends on your review question, the risk of selective publication, the likely location of missing studies, and whether finding them could realistically change your conclusions.
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A paywalled journal article may have a legitimate open version elsewhere. Learn where to search, how to recognize different manuscript versions, and how to verify that the copy you find is the paper you actually need.
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An accepted manuscript has passed peer review but is not necessarily identical to the final published article. For many reading purposes it may contain the research you need, but post-acceptance changes, corrections, and citation details can sometimes make the version of record important.
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If you cannot access a research paper, contacting the author is a legitimate option and may result in a copy or an authorized access link. Learn whom to contact, how to make the request, and why the version an author can share may depend on publisher policies and publication rights.
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An institutional repository is a digital service used by a university or other organization to collect, preserve, and provide access to scholarly outputs created by its community. It may contain an accessible manuscript of a paper even when the publisher's version is behind a paywall.
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A paper uploaded to ResearchGate or Academia.edu is not automatically reliable or unreliable simply because of where you found it. Verify the paper's identity, publication status, manuscript version, provenance, and current scholarly record before relying on the uploaded file.
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Finding a citation does not mean the full paper is available in the database where you found it. Verify the reference, search systematically across publisher, repository, and library routes, and do not treat an abstract or another author's description as a substitute for reading the original.
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Reading an abstract can establish that a paper exists and provide a concise account of its purpose and reported findings, but it rarely gives enough information to evaluate the study fully. Whether you should cite it depends on the claim you are making and whether the abstract actually supports that claim.
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If you know a study only because another paper describes or cites it, you have not consulted the original study. Find and read the original whenever reasonably possible; if you cannot, make the secondary route visible rather than citing the original as though you read it yourself.
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Secondary citation makes it explicit that you learned about an original source through another work rather than consulting the original yourself. It can be appropriate when the original genuinely cannot be obtained, but it should usually remain a fallback rather than a shortcut around reading accessible sources.
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A language barrier does not automatically make an important research source unusable. Translation tools can help you determine relevance and sometimes understand substantial portions of a paper, but important methodological, numerical, or interpretive claims may require verification by a fluent reader or reliable human translation.
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