Removing linked files in EXCEL

I have set up a work book with 3 linked files. Over a period of time 1 of the linked files is now obsolete. Now when I open the file I am told to open the obsolete linked file. Using EDIT menu hitting the LINKS option sure enough the obsolete file is listed. The options available only include CREATE UPDATE CHANGE SOURCE. HOW DO I REMOVE THIS OBSOLETE FILE FROM THE LINKS ? Please note I have removed all references to this file in the worksheets of the workbook.
Thanking you in anticipation
Ian Clark