Creating a bibliography from more than one EndNote library for document is possible but not recommended for large documents as various problems may occur.

There may be duplicate records in each library and EndNote will not be able to format a reference with two different identification numbers. What may be {Smith 1987, #345} in one library may be {Smith 1987, #200} in another.

Its best to merge separate libraries before inserting temporary EndNote citations

To Import one EndNote library into another

• Open EndNote, open the library into which you want to import the references.
• Go to File > Import > Choose File, and open the EndNote Library
• Select the file and click OK. Then select EndNote Library as your import option from the Import Options list.
• Select an option from the Duplicates list. (Import All is a good fail-safe option.)
• Click Import.

You can also simply copy references from one library to another

• Highlight the references in one library, and choose Copy (Ctrl+C).
• (Hold down the Ctrl key to select non-consecutive references, and use the Shift key to select a range.)
• Open the library to which you want to add the references and choose Paste (Ctrl+V).