@Override
  public void referenceRemoved() {
    super.referenceRemoved();

    for (RefClass subClass : getSubClasses()) {
      ((RefClassImpl)subClass).removeBaseClass(this);
    }

    for (RefClass superClass : getBaseClasses()) {
      ((RefClassImpl)superClass).removeSubClass(this);
    }
  }
@Override
  public void referenceRemoved()