Studies versus reports of studies

Systematic reviews have studies as the primary units of interest and analysis. However, a single study may have more than one report about it and each of these reports may contribute useful information for the review (see Chapter 7, Section 7.2). For most of the sources listed in Section 6.2, the search process will retrieve individual reports of studies, however there are some study-based resources, such as trials registers and trials results databases (see Sections to