that the set does not have a label. A string of length 0 is also
written if LABELSOURCE=VARLABEL was specified.
-@item
-A space.
-
@item
The short names of the variables in the set, converted to lowercase,
-each separated from the previous by a single space.
+each preceded by a single space.
Even though a multiple response set must have at least two variables,
some system files contain multiple response sets with no variables or