SQL & PL/SQL :: Populate Tables Of Ref

I like to the following:

Objects: Car, Person

Person can own a lot of cars which i like to implement as table of ref in person!

When i poluplate the ref table, I always get null-references! Compiler is ok, no syntax errors or anything else

drop table person_tab;
drop table car_tab;
drop type person_type force;
drop type car_type force;
drop type owns_type force;

---------------------------Objects-----------------------------

create or replace type car_type as object
(cartype varchar2(10),
byear integer
);
/

create or replace type owns_type
as table of ref car_type;
/

create or replace type person_type as object
(fname varchar2(10),
owns owns_type
);
/

commit;

--------------------------Object Tabs--------------------------

create table person_tab of person_type
(fname primary key)
nested table owns store as owns_cars;
/

create table car_tab of car_type
(cartype Primary Key
);
/

commit;

------------------------Populate Tables------------------------

insert into person_tab values
('meier', owns_type());
/
insert into car_tab values
('audi', 2011);
/
insert into car_tab values
('vw', 2012);
/
insert into car_tab values
('bmw', 2011);

commit;

----------------------Populate Ref Tables----------------------

insert into table
(select p.owns
from person_tab p
where p.fname = 'meier')
select ref (c)
from car_tab c
where c.cartype = 'audi';
/

insert into table
(select p.owns
from person_tab p
where p.fname = 'meier')
select ref (c)
from car_tab c
where c.cartype = 'vw';
/
commit;