EJB / EE :: Relation Between Entity On Server And In Library

I have the following problem:

I need to make a relation (OneToMany) between a entity on my server and a entity in my library (ManyToOne).

My program consists of 3 main components:

- a client (who uses session beans to query the server)
- a server (which contains entity's)
- a lib which is shared between the client and the server. (which also contains entity's)

Here is the thing I want to do:

Class on my Server:

@Entity
public class ClassOnServer implements Serializable{
@Id
private int uid;
@OneToMany(cascade=ALL, mappedBy="relation")
private Set<ClassOnServer> relation1; //This is no problem, because the server can import the library
}

Class on my Library:

@Entity
public class ClassInLibrary implements Serializable{
@Id
private int uid;
@ManyToOne
private ClassOnServer relation2; //This gives an error because ClassOnServer can not be imported into the library
}

It's not an option to move ClassOnServer to my lib because this would ruin the whole architecture.