Intermediate

;; An SXML is: (cons Symbol LSXML)
;;
;; A LSXML is one of:
;; -- empty
;; -- (cons String LSXML)
;; -- (conns SXML LSXML)
;;
;; interpretation: an SXML corresponds to a pair of tags, 
;; designated by the leading Symbol; 
;;
;; a LSXML corresponds to the items that may appear 
;; between the start and end tag

Solution:

;; [PTS 2]
'(blockquote 
   "a"
   "b"
   (blockquote "c"
               "d")
   "e")

;; or 

(list 'blockquote 
      "a"
      "b"
       (list 'blockquote
             "c"
             "d")
       "e")

;; or with cons