doc: add a reference to the DNS Catalog Zones Internet Draft and a link to the trust anchor RFC

doc/configuration.rst

@@ -585,7 +585,8 @@ Catalog zones
 Catalog zone is a concept when the list of zones configured is maintained
 as contents of a special zone. This approach has the benefit of simple propagation
 of the actual zone list to slave servers. Especially when the list is frequently
-updated.
+updated. Currently, catalog zones are described in this `Internet Draft
+<https://tools.ietf.org/html/draft-ietf-dnsop-dns-catalog-zones>`_.
 
 Terminology first. *Catalog zone* is a meta-zone which shall not be a part
 of the DNS tree, but it contains information about the set of member zones and

doc/operation.rst

@@ -470,7 +470,7 @@ Special states for algorithm rollover:
 
 - ``post-active`` — The key is no longer published in the zone, but still used for signing.
 
-Special states for RFC 5011 trust anchor roll-over
+Special states for :rfc:`5011` trust anchor roll-over
 
 - ``revoke`` (only for KSK) — The key is published and used for signing, and the Revoked flag is set.