When a Cochrane Review (or a protocol) is published for the first time a new citation version is automatically generated. Cochrane Review citation versions are recorded in reference databases such as PubMed, MEDLINE, and Science Citation Index (SCI).
Protocols do not have citations in MEDLINE or SCI, but are included in other databases such as PROSPERO.
Occasionally, it may be necessary to split a protocol or review into two or more protocols or reviews, or merge two or more protocols or reviews to create a new protocol or review. Each of the new versions will have a new citation.
Each citation version is assigned a new digital object identifier (DOI); see Digital object identifier (DOI) and website address (URL) of a Cochrane Review.