Add informative reference to DID Core.

Author: msporny

index.html

@@ -619,14 +619,16 @@ <h2>Terminology</h2>
 [=verifiable credential=] and are associated with [=subjects=] such that a
 [=verifiable credential=] can be easily ported from one
 [=credential repository=] to another without reissuing the [=credential=].
-An example of a DID is `did:example:123456abcdef`.
+An example of a DID is `did:example:123456abcdef`. See the
+[[[?DID-CORE]]] specification for further details.
         </dd>
         <dt><dfn class="lint-ignore" data-lt="decentralized identifier documents|DID document|DID documents">decentralized identifier document</dfn></dt>
         <dd>
 Also referred to as a <strong><em>DID document</em></strong>, this is a document
 that is accessible using a [=verifiable data registry=] and contains
 information related to a specific [=decentralized identifier=], such as the
-associated [=credential repository=] and [=verification material=].
+associated [=credential repository=] and [=verification material=]. See the
+[[[?DID-CORE]]] specification for further details.
         </dd>
         <dt><dfn data-lt="default graph">default graph</dfn></dt>
         <dd>