public function page($page)
  {
    if (false === is_numeric($page) || $page <= 0)
    {
      throw new InvalidArgumentException(sprintf(
        '%s is an invalid page value. It has to be numeric and positive',
        $page
      ));
    }

    $this->responseConfig['optionalParameters'] = array_merge(
      $this->responseConfig['optionalParameters'],
      array("ItemPage" => $page)
    );

    return $this;
  }