EndNote has two methods for minimizing duplication of records. In your case when downloading references into an Endnote library select the “Automatically discard duplicates” option in the Duplicates section of Endnote preferences. This enables Endnote to automatically discard duplicate references when downloading from online databases. (Refer to attached image.) The second method is to compare and delete duplicate records after the downloading process is been completed.
For further information concerning duplicate references go to the Help section of Endnote toolbar and search for “Duplicate references”.
