change to DOI for referencing

Author: SteveLLamb

doc/main.html

@@ -531,7 +531,7 @@ <h4>Normative references section</h4>
 
           <p>Dated references may be used when referencing a specific element of the document is necessary, e.g., a table, or when past and future editions of the document are likely to be inadequate. </p>
 
-          <p class="note"><a href="#bib-ag-29"></a> specifies the persistent URIs for both the most recent and specific editions of a SMPTE document.</p>
+          <p class="note">DOI links should be used for both the most recent and specific editions of a SMPTE document. SMPTE HO can provide guidance for specific DOIs available.</p>
 
         <div class="example">
 <pre>&lt;section id=&quot;sec-normative-references&quot;&gt;