public function filterByDistance(\Tx_Oelib_List $unfilteredObjects, \Tx_Oelib_Interface_Geo $center, $distance)
    {
        $objectsWithinDistance = new \Tx_Oelib_List();

        /** @var \Tx_Oelib_Interface_Geo|\Tx_Oelib_Model $object */
        foreach ($unfilteredObjects as $object) {
            if ($this->calculateDistanceInKilometers($center, $object) <= $distance) {
                $objectsWithinDistance->add($object);
            }
        }

        return $objectsWithinDistance;
    }