 A journal can adopt editorial policies to increase its impact factor.For example, journals may publish a larger percentage of review articles which generally are cited more than research reports.Journals may also attempt to limit the number of "citable items"—i.e., the denominator of the impact factor equation—either by declining to publish articles that are unlikely to be cited (such as case reports in medical journals) or by altering articles (e.g., by not allowing an abstract or bibliography in hopes that Journal Citation Reports will not deem it a "citable item").