protected function _getOverride($format, $parameters = array())
    {
        $override = $format;

        $locale = $this->getLocale();

        if (!isset($this->_overrides[$locale])) {
            $this->_overrides[$locale] = array();
        }

        if ($parameters)
        {
            $key = $this->_getOverrideKey($format, $parameters);

            if (!isset($this->_overrides[$locale][$key]))
            {
                foreach ($this->_getOverrides($format, $parameters) as $candidate)
                {
                    // Check if the override is translatable.
                    if ($this->isTranslatable($candidate))
                    {
                        $override = $candidate;
                        break;
                    }
                }

                $this->_overrides[$locale][$key] = $override;
            }
            else $override = $this->_overrides[$locale][$key];
        }

        return $override;
    }