Literal comments and processing instructions are also allowed:
<?xml-stylesheet type="text/css" href="bibliography.css"?>,
<bib>
  <h1>Bibliography</h1>
 {
   for $b in doc("bib.xml")/bib/book
   return
      $b/title 
 }
</bib>,
<!-- An example from Elliotte Rusty Harold's 
  XQuery presentation -->
Notice the commas
Remember, an XQuery is not an XML document.