Corrected references to [XML10] and [HTML40].

Author: bert-github

selectors3/Overview.src.html

@@ -144,7 +144,7 @@ <h3 id=terminology>Terminology</h3>
   <a href="http://www.w3.org/TR/CSS21/conform.html#defs">Definitions</a>
   section of [[!CSS21]].
   Examples of document source code and fragments are given in XML
-  [[XML10] or HTML [[HTML40]]
+  [[XML10]] or HTML [[HTML40]]
   syntax.
 
   <h3 id=changesFromCSS2>Changes from CSS2</h3>