We recommend that you export the search results from every database you search for import into reference management program. Using the program you can gather all references and remove any duplicates. Remember to create reference lists before you start with deduplication.
The reference management software EndNote is commonly used for this because it can handle very large reference libraries, but there are other options. We compare some common ones in the Citation Guide.
There are specific methods for deduplication meant to increase accuracy compared to automatic deduplication by a reference management program. The following are some examples.