REFERENCES constraint

Two questions (maybe they are silly..)

1. Can a column reference more than one table? (This assumes you use a
single sequence to generate the IDs for both "tbla" and "tblb". I guess
you would also have the problem of enforcing a unique index. Say what?!
A unique index across multiple tables.. absurd :) eg..

CREATE TABLE blah (
id int4,
f_id int4 REFERENCES tbla (id) REFERENCES tblb (id)
)

2. Can a column reference another column in the same table? eg..

CREATE TABLE bloo (
id int4,
p_id int4 REFERENCES bloo (id)
-- or
--p_id int4 REFERENCES (id)
)

I'm guessing the answer is no, in which case I have to fall back to
writing custom PL/ functions and triggers. Just thought I'd ask anyway.
It would be nice if it were this easy though...

-Cedar
p.s. please CC my on this thread.. I'm on vacation (on this list) :0