Database searches are often supplemented by a manual search, i.e. handsearching. Handsearching can be used to find studies that are incompletely indexed in databases or otherwise not found in a database search.
How to handsearch
Carefully browse through the main scientific journals and other publications on a given topic. Perhaps you already know the key publications in your subject area or you can look at which journal titles appear most often in your search results.
