diff --git a/src/ixml-specification.html b/src/ixml-specification.html
index d8145c1b..f04b5839 100644
--- a/src/ixml-specification.html
+++ b/src/ixml-specification.html
@@ -765,8 +765,10 @@ <h2 id="serialisation"><a href="#serialisation">Constructing XML</a></h2>
 
 <h3 id="x-serialisation"><a href="#x-serialisation">Serialization</a></h3>
 
-<p>A conformant Invisible XML processor is required to produce well-formed XML
-output, but its choices in constructing the XML are not otherwise constrained.
+<p>A conformant Invisible XML processor is required to produce well-formed
+output [<a href="#xml">XML</a>]
+that is namespace well-formed [<a href="#xmlns">XMLNS</a>],
+but its choices in constructing the XML are not otherwise constrained.
 Processors <span class="conform">should</span> be capable of producing
 serialized XML as a character stream, but other forms (e.g. DOM instances or XDM
 instances) <span class="conform">may</span> also be used.</p>
@@ -1032,6 +1034,10 @@ <h2 id="references"><a href="#references">References</a></h2>
 Language (XML) 1.0 (Fifth Edition)</em>, W3C, 2008, <a
 href="https://www.w3.org/TR/xml/">https://www.w3.org/TR/xml/</a></p>
 
+<p id="xmlns">[XMLNS] Tim Bray <em>et al</em>. (eds.), <em>Namespaces
+in XML 1.0 (Third Edition)</em>, W3C, 2009, <a
+href="https://www.w3.org/TR/xml-names/">https://www.w3.org/TR/xml-names/</a></p>
+
 <h2 id="informational"><a href="#informational">Informational References</a></h2>
 
 <p id="cyk">[CYK] Sakai, Itiroo. <em>Syntax in universal translation</em>. In