"Further, the contents of any two matching tags must itself be valid
XML.": "contents" -> "content"

The book states that when
  scala.xml.XML.save("therm1.xml", node)

is called, that the output file, "therm1.xml", will have header:
  <?xml version='1.0' encoding='UTF-8'?>

But when I do that, in the same way the book describes, there is no xml
header, just pure XML inside the therm1.xml.