Research is often reported in the form of published journal articles. Databases such as PubMed, CINAHL, PsycINFO, Sociological Abstracts, ERIC, and Web of Knowledge gather this information into a searchable format. Databases have different producers, so the appearance of the search engines varies. To address the issue of information overload, other databases have been developed to help busy clinicians find summaries of research - secondary literature. These databases are listed first followed by databases which primarily present articles from research studies - the primary literature.