Обсуждение: Does "USING" work?

Tried this simple test without success.  psql says (\h SELECT) that it
should work.  Do I have the syntax wrong?

CREATE TABLE a(
 x INTEGER PRIMARY KEY
 , y INTEGER
);

CREATE TABLE a1(
 x INTEGER REFERENCES a(x)
 , z INTEGER
);

INSERT INTO a(x, y) VALUES (1, 1);
INSERT INTO a(x, y) VALUES (2, 2);
INSERT INTO a1(x, z) VALUES (2, 2);


SELECT a.x, a.y, a1.z
FROM USING( x )
WHERE a.x = a1.x
;

DROP TABLE a;
DROP TABLE a1;