private void referenceActionPerformed(ActionEvent e) {
   IndexItems indexItem = (IndexItems) super.getModel();
   if (reference.getSelectedIndex() == 0) {
     indexItem.setReference("");
   } else {
     ResourceUtils.PersistentId persistentID =
         (ResourceUtils.PersistentId) reference.getSelectedItem();
     indexItem.setReference(persistentID.getPersistentId());
   }
 }
 /**
  * Set the domain model for this editor.
  *
  * @param model the model
  */
 public void setModel(final DomainObject model, InfiniteProgressPanel progressPanel) {
   super.setModel(model, progressPanel);
   IndexItems indexItem = (IndexItems) super.getModel();
   reference.setModel(new DefaultComboBoxModel(ResourceUtils.getReferencesArray()));
   int selectedIndex = ResourceUtils.getIndexById(indexItem.getReference());
   if (selectedIndex >= 0) {
     // add 1 to account for the blank at the top of the list
     reference.setSelectedIndex(selectedIndex + 1);
   }
 }