+Normally, only a single case (for SD and SD., two cases) need be
+non-missing in each group for the aggregate variable to be
+non-missing. Specifying /MISSING=COLUMNWISE inverts this behavior, so
+that the aggregate variable becomes missing if any aggregated value is
+missing.
+
+If PRESORTED, DOCUMENT, or MISSING are specified, they must appear
+between OUTFILE and BREAK.
+
+At least one break variable must be specified on BREAK, a
+required subcommand. The values of these variables are used to divide
+the active file into groups to be summarized. In addition, at least
+one @var{dest_var} must be specified.
+