public function showThreadMessages($user_id, $thread_id)
    {
        if (!is_numeric($user_id) || 0 >= $user_id) {
            throw new InvalidArgumentException(
                "Api::showThreadMessages user_id field should be positive integer");
        }

        if (!is_numeric($user_id) || 0 >= $user_id) {
            throw new InvalidArgumentException(
                "Api::showThreadMessages thread_id field should be positive integer");
        }

        /* @var $command \Guzzle\Service\Command\AbstractCommand */
        $command = $this->client->getCommand(
            'ShowThreadMessages',array('id'=>$user_id,'thread_id'=>$thread_id));

        return $this->executeCommand($command);
    }