foreign keys - script

I'm also having a problem with my references.

In the script below, I get this error after each references statement:
NOTICE: CREATE TABLE/FOREIGN KEY clause ignored; not yet implemented

Any ideas?

drop table model_part;
drop table models;
drop table parts;
drop table category;
drop sequence model_part_model_part_id_seq;

create table category (
category_id char(5) primary key,
name varchar(20));

create table parts (
part_id char(10) primary key,
category_id char(5) references category
on delete cascade,
name varchar(20),
price numeric(7,2));

create table models (
model_id char(10) primary key,
name varchar(20),
description text);

create table model_part (
model_part_id serial,
part_id char(10) references parts
on delete cascade,
model_id char(10) references models
on delete cascade);

Adam Lang
Systems Engineer
Rutgers Casualty Insurance Company