Some features of EndNote Online are useful for detailed or systematic-style literature reviews
Panopto video from Academic Skills Centre, University of Birmingham (includes subtitles).
EndNote offers an easy way to find, compare and remove duplicate references.
Go to Organize - Find Duplicates
This will identify and auto-tick boxes against the duplicated items across all your references.
Note that this feature does not search for duplicate entries within individual Groups in Endnote Online.
EndNote online will allow you compare records and select the one with the best information. You can then delete the other references. You may wish to add them to another group first if you need to keep a copy of them.
To delete, rename and share groups of references, choose Organize thenManage My Groups