public function getPage($index)
 {
     $criteria = new Criteria();
     $criteria->add(QubitInformationObject::PARENT_ID, $this->informationObject->id);
     $criteria->addJoin(QubitInformationObject::ID, QubitDigitalObject::INFORMATION_OBJECT_ID);
     $criteria->setLimit(1);
     $criteria->setOffset($index);
     return QubitDigitalObject::getOne($criteria);
 }