src/Pure/Thy/html.scala

     XML.Elem(Markup("a", List("href" -> href)), if (body.isEmpty) text(href) else body)
 
   def image(src: String, alt: String = ""): XML.Elem =
     XML.Elem(Markup("img", List("src" -> src) ::: proper_string(alt).map("alt" -> _).toList), Nil)
 
-  def source(src: String): XML.Elem = pre("source", text(src))
+  def source(body: XML.Body): XML.Elem = pre("source", body)
+  def source(src: String): XML.Elem = source(text(src))
 
   def style(s: String): XML.Elem = XML.elem("style", text(s))
 
   def style_file(href: String): XML.Elem =
     XML.Elem(Markup("link", List("rel" -> "stylesheet", "type" -> "text/css", "href" -> href)), Nil)