protected function _replaceBigPrefixes($string)
    {
        foreach ($this->BIG_PREFIXES as $bp => $bp_replacement) {
            $string = preg_replace_callback(
                '/(\d*) *' . $bp . '(\d?)/i',
                function ($m) use ($bp_replacement) {
                    $factor = (int)$m[1];
                    if (!$factor) {
                        $factor = 1;
                    }
                    return ($bp_replacement * $factor)
                        . ($bp_replacement == 100 ? ($m[2] ? 'und' : '') : 'und')
                        . $m[2];
                },
                $string
            );
            $string = $this->_andition($string);
        }
        return $string;
    }