two entities having relationship but they are not in the same ejb

I have entity A in ejb a and entity B in ejb b and one ear project wich contains the two ejb plus one app swing client.

@entity
public class A{                 
    //attributes
    @oneToOne
    B b;
 }
 @entity
 public class B{                 
    //attributes 
 }

I want to know how to do this if they are not in the same ejb.
Thanks for you all