CREATE TABLE with foreign key and primary key

I'm trying to create a table that has three fields as primary key. These
fields must exist in two other tables. id_aluno is primary key in table
pessoa, id_curso and id_polo are primary key in table curso_polo. But it
seems it won't work. What am I doing wrong? See definitions below.
Specifically, I didn't understand:
NOTICE:  Illegal FOREIGN KEY definition REFERENCES "curso_polo"
ERROR:  number of key attributes in referenced table must be equal to
foreign key

I'm using PostgreSQL 7.0

ufgvirtual=# create table matricula (
ufgvirtual(# id_aluno char(15) references pessoa,
ufgvirtual(# id_curso int4 references curso_polo,
ufgvirtual(# id_polo int2 references curso_polo,
ufgvirtual(# local_prova varchar(50) not null,
ufgvirtual(# autorizado bool default 'f' not null,
ufgvirtual(# id_plano_pgto int2 references plano_pgto not null,
ufgvirtual(# data_matricula date default CURRENT_DATE not null,
ufgvirtual(# primary key(id_aluno,id_curso,id_polo));
NOTICE:  CREATE TABLE/PRIMARY KEY will create implicit index
'matricula_pkey' for table 'matricula'
NOTICE:  CREATE TABLE will create implicit trigger(s) for FOREIGN KEY
check(s)
NOTICE:  Illegal FOREIGN KEY definition REFERENCES "curso_polo"
ERROR:  number of key attributes in referenced table must be equal to
foreign key
                              Table "pessoa"  Attribute   |   Type   |                    Modifier
---------------+----------+-------------------------------------------------login         | char(15) | not nullnome
    | char(50) | not null
 
.
.
.
        Table "curso_polo"  Attribute   |   Type   | Modifier
---------------+----------+----------id_curso      | integer  | not nullid_polo       | smallint | not nullcoordenador
| integer  | not nulldata_limite   | date     |id_plano_pgto | smallint |num_vagas     | integer  | not null
 


I have tables pessoa, curso, polo, curso_polo and matricula. Primary key in
curso_polo are id_curso (references curso) and id_polo (references polo). In
table matricula I want as primary key id_pessoa (references pessoa),
id_curso (references curso_polo) and id_polo (references curso_polo).

I hope I have provided enough information. I'm a little confused.



Paulo R. Siqueira