Cochrane review authors should seek advice from their Trials Search Co-ordinator on sources to search.
CENTRAL is considered to be the best single source of reports of trials for inclusion in Cochrane reviews.
The three bibliographic databases generally considered to be the most important sources to search for studies for inclusion in Cochrane reviews are CENTRAL, MEDLINE and EMBASE.
National, regional and subject-specific databases should be selected for searching according to the topic of the review.
Conference abstracts and other grey literature can be an important source of studies for inclusion in reviews.
Reference lists in other reviews, guidelines, included (and excluded) studies and other related articles should be searched for additional studies.
Efforts should be made to identify unpublished studies.
Ongoing trials should be identified and tracked for possible inclusion in reviews on completion.
Trials registers and trials results registers are an important source of ongoing and unpublished trials.