public function administrativeArea($admin_area_id, Request $request = null)
    {
        $admin_area = AdministrativeArea::find($admin_area_id);

        if ($request) {
            $included = [];
            if (
            $request->has('include') &&
            AdministrativeArea::isIncludable($request->include)
            ) {
                $cities = $admin_area->cities()->getQuery();
                $cities_included = new Collection($cities, 'city');
                $included = $cities_included->toArray();
            }
            $links = $request ? ['self' => $request->url()] : [];
            return $this->respondWithItem(
                $admin_area,
                'administrative_area',
                $links,
                $included
            );
        }
        return $admin_area;
    }