You can use the following form for an external record:

    $group-name object = value [object = value]...$[END]

    group-name  Is the name of the group containing the objects
                to be given values. The name must have been
                previously defined in a NAMELIST statement in
                the scoping unit.

    object      Is the name (or subobject designator) of an
                entity defined in the NAMELIST declaration of
                the group name. The object name must not contain
                embedded blanks, but it can be preceded or
                followed by blanks.

    value       Is a null value, a constant (or list of constants),
                a repetition of constants in the form r*c, or a
                repetition of null values in the form r*.

  If more than one object=value or more than one value is specified,
  they must be separated by value separators.

  A value separator is any number of blanks, or a comma or slash,
  preceded or followed by any number of blanks.

  Comments (beginning with !  only) can appear anywhere in namelist
  input.  The comment extends to the end of the source line.