Every .dk domain that delegates its _acme-challenge name to 554ba7f4-b26e-4b9f-9bd6-3962e80a35a4.3.authorize.certificatemanager.goog. Such CNAMEs hand DNS-01 certificate validation to a shared service, so this list shows who issues TLS certificates through it. Data comes from our own scanners, which re-resolve every .dk domain in the zone roughly once a week.