To close a currently open reference, do any of the following:
Click in the close button on the Reference window.
From the File menu, select Close Reference.
To close one reference and view the next or previous reference in the library, use the Next Reference and Previous Reference commands on the References menu (or the buttons in the Reference window). See Previous and Next Reference Commands.
Close all open references by holding down the Shift key while pressing Ctrl+W. Close all open windows with just one click by pressing the Option key when clicking the close button.
Note: All data in a reference is automatically saved when you close the Reference window.