public function thumbnails($path, $size = 'small', $format = 'jpeg', $sandbox = false)
        {
            // build url
            $url = '1/thumbnails/';
            $url .= ($sandbox) ? 'sandbox/' : 'dropbox/';
            $url .= trim((string) $path, '/');

            // build parameters
            $parameters['size'] = (string) $size;
            $parameters['format'] = (string) $format;

            // make the call
            return $this->doCall($url, $parameters, 'GET', null, false, true);
        }