1> (define doc-ast 
    (html
     (head (title "Demo Links"))
     (body
       ...)))

2 > (extract-links doc-ast)
("http://www.acm.org/dl" "http://www.ieee.org/ieeexplore/" "http://www.w3c.org"
 "http://link.springer.de/link/service/series/0558/" "http://www.cs.auc.dk"
 "http://www.auc.dk")