some of the unsung heroes of 20th century 
(ROOT (NP (NP (DT some)) (PP (IN of) (NP (NP (DT the) (JJ unsung) (NNS heroes)) (PP (IN of) (NP (JJ 20th) (NN century)))))))
(ROOT (NP (NP (DT )) (PP (IN ) (NP (NP (DT ) (JJ ) (NNS )) (PP (IN ) (NP (JJ ) (NN )))))))