CMS operates on your library search list by searching
  through the library (or libraries) in the list.  If you
  have more than one library in the search list, CMS
  searches the libraries one at a time, in the order in
  which they appear in the search list, until a specified
  object is found.  Once the object is found, CMS performs
  the specified operation on the object. CMS will not
  continue to search for the object in any of the remaining
  libraries.

  When an object with the same name exists in more than one
  library in the library search list, CMS processes only
  the first occurrence of the specified object and ignores
  any later instances of that object in subsequent
  libraries.  Thus, the first instance of the object
  occludes any subsequent instances of that object.

  You can direct CMS to search for all occurrences of an
  object by deactivating occlusion for the object.