The Input Sources Selection list box specifies the list of sources to
 choose from to add to the left-hand list box.

 By default, the list will contain files which are found in the current
 default directory.

 Files can be moved to the left-hand list in three ways:

     o double-click on a file specification

     o highlight a file specification, then click on the left arrow button

     o click on the All button, which will move all the files from the
        right-hand box to the left-hand box