public static function getFilenames(Config $config, $part)
    {
        $extensions = implode('|', array_map('preg_quote', $config['valid_content_extensions'])) . '|html';

        $raw = preg_replace('/(.*)?\\.(' . $extensions . ')$/', '$1', $part);
        $raw = Builder::removeSortingInformations($raw);

        return ["$raw.html", $raw];
    }