White space suppress markers:   
(paper
   (author "Kurt Normark")
   (title "The Duality of" (em "XML Markup") "and"
          (em "Programming Notation") _ "."))

Semi constant strings:
(paper
  (author [Kurt Normark] )
  (title [The Duality of ,(em [XML Markup]) and
         ,(em [Programming Notation]).] ))

Attributes as keyword parameters:
(body 
  "This is a"
  (a  'href  "http://www.w3c.org"  'target  "main"  "link")
  "to the W3C site.")