public function getMonthNamesNarrow($month = null)
    {
        $calendar = $this->getName();
        // gregorian, generic

        $data = array();
        $calendsFallback = array($calendar, 'gregorian', 'generic');
        foreach ($calendsFallback as $calendar) {
            $data = $this->getRepoReader()->getEntityByPath(
                'dates/calendars/calendar[@type="'.$calendar.'"]/months/monthContext[@type="format"]/monthWidth[@type="abbreviated"]/month'
            );

            if ($data) {
                break;
            }
        }

        $months = array();
        foreach($data as $d) {
            $months[$d['type']] = $d['value'];
        }

        $return = ($month == null) ? $months : false;

        return isset($months[$month]) ? $months[$month] : $return;
    }