+void covariance_accumulate (struct hsh_table *, struct moments1 **,
+ const struct ccase *, const struct variable **, size_t);
+struct hsh_table * covariance_hsh_create (size_t);
+struct design_matrix * covariance_accumulator_to_matrix (struct hsh_table *, const struct moments1 **,
+ const struct variable **, size_t, size_t);