Duplicate references can cause a number of issues in the creation of a bibliography. If both instances are cited in your paper, they will show up twice in the bibliography, even though they are the same citation.
Notice that we have several duplicates in our "New Project" folder.
To remove duplicates, click on "More" in the top menu.
Select "Find duplicates."
A pop up will appear. Select "All references in 'your project title'" and "strict match." Select "Find duplicates."