code: public final ReadOnlyObjectProperty<Entry<T>> recurrenceSourceProperty() {
          if (recurrenceSource == null) {
              recurrenceSource = new ReadOnlyObjectWrapper<Entry<T>>(this, "recurrenceSource") { //$NON-NLS-1$
                  @Override
                  public void set(Entry<T> newEntry) {
                      super.set(newEntry);
                      if (newEntry != null) {
                          setRecurrence(true);
                      } else {
                          setRecurrence(false);
                      }
                  }
              };
          }
  
          return recurrenceSource.getReadOnlyProperty();
      }
docs: If the entry is a recurrence (see {@link #recurrenceProperty()}) then
  this property will store a reference to the entry for which the
  recurrence was created.
  
  @return the entry that was the source of the recurrence