public function getPurchaseHistoryURI($params = array()) {
        $default_params = array(
            'client_id' => $this->getClientID(),
            'response_type' => 'code',
            'redirect_uri' => $this->getCurrentURI(),
        );
        if ($this->xiti) {
            $default_params['xiti_json'] = $this->getXitiConfiguration();
        }
        $default_params['v'] = self::VERSION;
        return $this->getUrl('www', 'account/purchasehistory', array_merge($default_params, $params));
    }