As you build your Zotero library you may start to have duplicate references. To view all of the duplicates go to the end of your list of collections on the panel on the left and select Duplicate Items. The items that Zotero believes are duplicates will appear in the center panel. Select the reference to view details in the panel on the right.
The best way to remove duplicates is to merge them. Merging will retain all of the collections and tags of the merged items. If all of the fields of the duplicates do not match, you can select one of the items to be the master by making a selection in the right panel under Choose the version of the items to use as the master item.
