Information regarding foriegn key constraint.

Dear Sir,
I am a Graduate student at the University of Toledo.My Master's project
involves creating a database  in PostgreSQL version 6.5.3.I was wondering
if I can use SERIAL key along with a PRIMARY key as follows:

create table ohiouniv (uid serial primary key,
                        uname varchar(45) not null,
                        ucity varchar(25) not null);

create table departments (deptid serial primary key,
                           deptshrtn varchar(10) not null,
                           deptfulln varchar(45) not null,
                           deptphone int8 unique not null check(deptphone>0));

When I tried giving the following for linking the above 2 tables:

create table univdept (uid integer references ohiouniv,
                                     deptid integer references departments);

The error was:
create table/foreign key clause ignored; not yet implemented

Does this mean we cannot use the foreign key constraint in this version of
PostgreSQL, and if so, what is the alternative for the above problem.Please
let me know about this at your earliest convinience.
Thanks much!
Best Regards
Meeta Bhate
University of Toledo.
EECS Department.
Ph:419 450 3685.