SQL REF Oracle Error

Question

Using some types which i will show below:

CREATE TYPE Course_objtype AS OBJECT (
Course_code VARCHAR2(4),
Course_name VARCHAR2(200),
Study_mode CHAR(2),
Campus REF Campus_list,
Faculty REF Faculty_list,
Director REF Staff_list
);

CREATE TYPE Campus_objtype AS OBJECT (
    Campus_ID NUMBER,
    Campus_code CHAR(1),
    Campus_name VARCHAR2(11),
    Phone_Number VARCHAR(20),
    Address Address_objtype
);

CREATE TYPE Faculty_objtype AS OBJECT (
Faculty_ID NUMBER,
Faculty_Name VARCHAR(200)
);

CREATE TYPE Staff_objtype AS OBJECT(
Staff_ID VARCHAR(7),
Person Person_objtype,
Staff_email VARCHAR2(200),
Office VARCHAR2(6),
Phone VARCHAR2(20),
Position VARCHAR2(15)
);

I've been trying to insert the values below into a table called Course_list, inheriting values from tables linked to the types above:

 INSERT INTO Course_list VALUES (
    '2136','Computing','FT',
    (SELECT REF(d) FROM Campus_list d WHERE d.Campus_code = 'C'),
    (SELECT REF(a) FROM Faculty_list a WHERE a.Faculty_ID = '3'),
    (SELECT REF(n) FROM Staff_list n WHERE n.Staff_ID = 'E129675')
);

Which brings me back the following error:

ORA-22979: cannot INSERT object view REF or user-defined REF

Any thoughts? I am clueless :(