minor grammar tweak

index.html

@@ -745,7 +745,7 @@ <h3>Primary Entry Page</h3>
 				<p>The <dfn>primary entry page</dfn> represents the preferred starting <a href="#wp-resources"
 						>resource</a> for a Web Publication and enables discovery of its <a>manifest</a>. It is the
 					resource that is returned when accessing the Web Publication's <a>address</a>, and MUST be included
-					either in the <a>default reading order</a> or <a>resource list</a>.</p>
+					in either the <a>default reading order</a> or the <a>resource list</a>.</p>
 
 				<p>Although any resource can link to the Web Publication manifest, the primary entry page typically
 					introduces the publication and provides access to the content. It might contain all the content, in