@Override
  public synchronized void addOutReference(RefElement refElement) {
    List<RefElement> outReferences = myOutReferences;
    if (outReferences == null) {
      myOutReferences = outReferences = new ArrayList<>(1);
    }
    if (!outReferences.contains(refElement)) {
      outReferences.add(refElement);
    }
  }
@Override
  public synchronized void addOutReference(RefElement refElement)