Added note that readers should understand the graph isomorphism problem.

--- a/spec/latest/rdf-graph-normalization/index.html Sun Oct 16 00:50:20 2011 -0400
+++ b/spec/latest/rdf-graph-normalization/index.html Sun Oct 16 01:08:39 2011 -0400
@@ -326,8 +326,9 @@
<p>
To understand the basics in this specification you must be familiar with basic
RDF concepts [[!RDF-CONCEPTS]]. A working knowledge of
-<a href="http://en.wikipedia.org/wiki/Graph_theory">graph theory</a> is
-also recommended.</p>
+<a href="http://en.wikipedia.org/wiki/Graph_theory">graph theory</a> and
+<a href="http://en.wikipedia.org/wiki/Graph_isomorphism">graph isomorphisms</a>
+is also recommended.</p>
</section>
<section>