A study of the references used in Cochrane protocols and reviews : Three bibles, three dictionaries, and nearly 25,000 other things

To describe the types of report that are cited by protocols and reviews included in the Cochrane Database of Systematic Reviews. The citation for each reference included in the Cochrane protocols and reviews published in the Cochrane Database of Systematic Reviews in issue 1, 1999 of The Cochrane Library were categorized by reference type (e.g., journal article, conference proceeding, book chapter, personal communication, Cochrane review). Of a total of 24,913 citations, 21,694 (87.1%) were references to journal articles. There was a significant difference between the proportion of references to studies that were journal articles (12,348 of 13,472; 91.7%) and the proportion of other references in this category (9,346 of 11,441; 81.7%). The great majority of studies included in Cochrane reviews at the beginning of 1999 had been published as journal articles.