REFERENCES in a field

Hi!
When I try to insert a FOREIGN KEY in a field while I'm create a table
with psql in the form:

create table table (
field1 CHAR(10) PRIMARY KEY,
field2 CHAR(10) REFERENCES table0
);

psql returns an error that tells "FOREIGN KEYS not implemented yet".
I'm running Postgres version 6.5.3, which version supports foreign keys?

Thank you,
Fernando