def delta_crl_distribution_points(self):
        """
        Returns delta CRL URLs - does not include complete CRLs

        :return:
            A list of zero or more DistributionPoint objects
        """

        if self._delta_crl_distribution_points is None:
            self._delta_crl_distribution_points = self._get_http_crl_distribution_points(self.freshest_crl_value)
        return self._delta_crl_distribution_points