Reference Type in PostgreSQL

Hello all, I'm new in PostgreSQL...

I would want to know like PostgreSQL manages the type reference that defines
the standard SQL:1999. I want to define the type of attribute like a
reference at other type.

For example, in Oracle8i the definition is:

-- Type Department
CREATE OR REPLACE TYPE Department_type AS OBJECT (
code NUMBER(5),
name VARCHAR(40)
);

-- Type Employee
CREATE OR REPLACE TYPE Employee_type AS OBJECT (
code NUMBER(5),
name VARCHAR2(40),
department REF Department_type -- Reference to Department object type
);

* *
How can I define it in PostgreSQL? I haven't found it in the manuals.

Thank you for help.

--
Elena

--
Elena