Table 6 ENTREQ items relating to literature searching

3 approach to searching

Indicate whether search was pre-planned or iterative; using comprehensive or theoretical sampling

S—sampling strategy

4 inclusion criteria

Specify inclusion/exclusion criteria (e.g. in terms of population, language, year limits, type of publication, study type)

T—type of studies

R—range of years

L—limits

I—inclusions/exclusions

5 data sources

Describe information sources used (e.g. electronic databases)

E—electronic sources

A—approaches

6 electronic search strategy

Describe literature search (e.g. provide electronic search strategies and search limits)

T—terms used