EndNote can search PubMed and Web of Science for updates and corrections to references already in your library. This feature will only work for references that have a DOI, or reliable entries in the author, journal title, and year of publication fields that it can match on.
Select an individual reference or a small group of references to check, and then go to References > Find References Updates.
EndNote will search for any changes and if any are found will display a side by side comparison:
Scroll through and compare the changes and decide if the updates are needed for your reference. In some case the changes may not be needed, such as a change from using an author's full name to using only the initial of the first name. However, in other cases such as the addition of a DOI or a change in the ISSN number then accepting the updates are warranted.
Click the "Update All Fields" button to accept all changes in the reference, or click "Update Empty Fields" to update only the empty fields in your existing references with new data.
Remember to click "Save Updates" to save the changes.
Adding references from many different databases can lead to having the same reference 2 or more times in your EndNote library. Fortunately, EndNote has the ability to find and delete duplicate references from a library.
To locate duplicates in an EndNote library make sure you are in the All References group and go to References > Find Duplicates
References that EndNote thinks are duplicates will be put into a Duplicate References group and a new window will appear that allows you to review the duplicates one by one and decide whether to keep both references or delete one. Make sure you are not deleting a reference that is already cited in a document. The older (first entered) reference will always appear in the left column.
By default, references are considered duplicates if they have the same reference type (such as Journal Article or Book), and the Author, Year, and Title fields are identical. The criteria for detecting duplicates can be changed in EndNote's preferences settings. Go to Edit > Preferences.
Select "Duplicates" from the options on the left and check or uncheck the boxes next to the fields that EndNote will compare to decide whether a duplicate reference exists.