How do I do a simple WHERE with foreign keys using SQLitePersistentObjects?

Question

I have two entities deriving from SQLitePersistentObject.

@interface EntityA : SQLitePersistentObject {   
    //stuff goeshere 
}

and

@interface EntityB : SQLitePersistentObject {
    EntityA *fk;
}
@property (nonatomic, retain)EntityA *fk;

How do I find all instances of EntityB whose fk is a specified instance of EntityA?