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