Hibernate mapping problem

Hi,

I've having trouble mapping a class with a composite key, part or all
of which are foreign keys, with a many-to-one relationship

class Mod {
private Integer codNum;
private Integer podNum;
}

class Cod {
private Integer codNum;
}

class Pod {
private Integer podNum;
}

The primary key of Mod is composed of codNum and podNum, which are
foreign keys to Pod and Cod, where Mod <- many-to-one -> Cod, and Mod
<- many-to-one -> Pod

If this is Mod.hbm.xml
<composite-id>
<key-property name="codNum" type="integer" column="cod_num" />
<key-property name="podNum" type="integer" column="pod_num" />
</composite-id>

How can I express the many-to-one relationship(s) and the class each
property belongs to?

Thanks

.