Knowing where to look for studies is key to a successful review. Below you will find information on the most relevant databases, as well as places to search for unpublished literature and a guide to hand searching.
The following are a selection of additional databases that should be searched in order to reduce language biases:
There are additional databases you will want to search depending on your subject.
Below you will find a sampling of selected subject-specific databases. Contact your librarian for information on additional databases.
To prevent publication bias, you need to search for grey (or gray) literature, that is, literature that has not been published.
The list of databases below is a good place to start; you should also look at conference abstracts as well as institutional and disciplinary repositories.
Hand searching is done to find studies that may not have been indexed in the databases. It is a manual process of looking through journals page by page; it often also involves looking at each reference in each journal article found.
You should hand search conference papers as well as the most relevant journals in your field.
Make sure you document the hand searching process.
Ask your librarian for assistance.
To learn more about why hand searching is so important, read this 2005 article from Armstrong et al.: It's in your hands: The value of hand searching...
Cochrane offers information on hand searching as well.