**
     * Registers the plugin specific rewrite rules
     *
     * Combined: sitemap(-+([a-zA-Z0-9_-]+))?\.(xml|html)(.gz)?$
     *
     * @since 4.0
     * @param $wpRules Array of existing rewrite rules
     * @return Array An array containing the new rewrite rules
     */
    public static function AddRewriteRules($wpRules) {
        $smRules = array(
            'sitemap(-+([a-zA-Z0-9_-]+))?\.xml$' => 'index.php?xml_sitemap=params=$matches[2]',
            'sitemap(-+([a-zA-Z0-9_-]+))?\.xml\.gz$' => 'index.php?xml_sitemap=params=$matches[2];zip=true',
            'sitemap(-+([a-zA-Z0-9_-]+))?\.html$' => 'index.php?xml_sitemap=params=$matches[2];html=true',
            'sitemap(-+([a-zA-Z0-9_-]+))?\.html.gz$' => 'index.php?xml_sitemap=params=$matches[2];html=true;zip=true'
        );
        return array_merge($smRules,$wpRules);
    }