BN_copy() returns B<to> on success, NULL on error. BN_dup() returns
the new B<BIGNUM>, and NULL on error. The error codes can be obtained
-by ERR_get_error(3).
+by L<ERR_get_error(3)|ERR_get_error(3)>.
=head1 SEE ALSO
-bn(3), err(3)
+L<bn(3)|bn(3)>, L<ERR_get_error(3)|ERR_get_error(3)>
=head1 HISTORY