EndNote offers a Find Duplicates command to help locate duplicate references. This command searches the references that are currently showing in the Library window to identify duplicates.
To find all of the duplicate references in a library:
Differences between reference fields are shown with blue highlighting. In addition, EndNote takes you to the first reference field in which there is dissimilar content between the two duplicate references. Scroll through the list to see which fields contain duplicate content and which contain dissimilar content.
For each set of duplicates, you have the option to:
Warning: The older (first entered) reference will always appear in the left column. Before selecting Keep This Record, which will delete the duplicate, check the record numbers to be sure that you are not deleting a reference already cited in a paper.