protected function addCacheBuster($sAsset)
    {
        if ($this->sCacheBuster) {

            $aParsedUrl = parse_url($sAsset);

            if (empty($aParsedUrl['query'])) {

                $sAsset .= '?';

            } else {

                $sAsset .= '&';
            }

            $sAsset .= 'revision=' . $this->sCacheBuster;
        }

        return $sAsset;
    }