4. Searching supplementary sources

Author(s)

Authors should check the reference lists of articles obtained (including those from previously published systematic reviews) to identify relevant reports. The process of following up references from one article to another is generally an efficient means of identifying studies for possible inclusion in a review.
Because investigators may selectively cite studies with positive results (Gotzsche 1987; Ravnskov 1992), reference lists should never be used as a sole approach to identifying reports for a review, but rather as an adjunct to other approaches.

Several electronic sources provide a "Find related" functionality. This functionality is often based on a poorly detailed (and thus difficult to describe and reproduce) algorithm (using theseaurus terms, keywords, ...). Therefore, we recommend to list the identified supplemental references under "Related citations".
Several electronic sources provide a "find citing articles" functionality. This functionality is often related to the quality of the references provided by the authors and thus not always exact. Therefore, we recommend to list the identified supplemental references under "Citing articles".