public function elementsOverviewAction ($elementType)
    {
        try
        {
            $elementReferences = array_map(
                function (Element $element)
                {
                    return $element->getReference();
                },
                $this->elementTypesModel->getListedElements($elementType)
            );

            return $this->twig->render("@core/elements_overview_page.twig", [
                "elementReferences" => $elementReferences
            ]);
        }
        catch (\InvalidArgumentException $e)
        {
            throw new NotFoundHttpException("Unknown element type '{$elementType}'.", $e);
        }
    }