(def sentences
  (->> (->  (slurp "http://www.news.com")    ; open url
            (strip-html)                     ; remove html
            (str/split #"\."))               ; split by sentence
        (map (comp str/trim str/lower-case)) ; feed through lower-case and trim
        set))                                ; transform into set

Result:
ArityException Wrong number of args (0) passed to: PersistentHashSet  clojure.lang.AFn.throwArity (AF
n.java:429)