public function getHyperlink($hyperlinkIndex)
    {
        if ($hyperlinkIndex == '')
            throw new Exception('Hyperlink index not specified');
        
        //build URI
        $strURI = Product::$baseProductUri . '/words/' . $this->getFileName() . '/hyperlinks/' . $hyperlinkIndex;

        //sign URI
        $signedURI = Utils::sign($strURI);

        $responseStream = Utils::processCommand($signedURI, 'GET', '', '');

        $json = json_decode($responseStream);        

        if ($json->Code == 200) {
            return $json->Hyperlink;
        }
        
        AsposeApp::getLogger()->warning('Error occured, http 200 code was not found.', array(
            'json-code' => $json->Code,
        ));
        return false;
    }