Literature Search

Literature Search

The What Works Clearinghouse (WWC) literature search is comprehensive and systematic. Detailed protocols guide the entire literature search process. At the beginning of the process, relevant journals, organizations, and experts are identified. The WWC searches core sources and additional topic-specific sources identified by members of the review team. The process is fully and publicly documented.

Trained WWC staff members use the following strategies in collecting studies:


Hand Searches: hand search the past 20 years (on average) of core journals relevant to all topics plus topic-relevant journals;

Electronic Databases: identify keywords for each topic and search a variety of electronic databases for relevant studies;

Submissions: incorporate studies submitted by the public;

Conference Proceedings: search the conference proceedings of core and topic-relevant associations; contact individuals with potentially relevant presentations for their papers;

Website Searches: search the websites of core and topic-relevant organizations and collect potentially relevant studies; and

Extensive Outreach: contact topic experts and relevant organizations to request studies as well as to request recommendations of other people and organizations that are able to provide studies.
The collected studies are screened first for relevance to the topic followed by a basic methodology screening. The studies that remain go through a more rigorous methodology screening. Those studies that meet the threshold relevancy and methodology criteria are then reviewed against the WWC Evidence Standards.