1. Click on the All Documents in the My Library pane on the left.
2. Click Tools and select Check for Duplicates.
A list of all documents that Mendeley identifies as being possible duplicates will be displayed.
Mendeley sometimes removes exact duplicates automatically.
3. You can merge the duplicate references by clicking on Confirm Merge in the Details pane on the right.
It is important first to check the referencing information for the documents.
4. Double-click on a duplicate to reveal the references Mendeley has identified.
5. Click on these identified documents to view their referencing information in the Details pane on the right, then compare the information between them.
6. Once done, choose either: