set the women 's liberation movement back 20 years 
(ROOT (S (VP (VB set) (NP (NP (DT the) (NNS women) (POS 's)) (NN liberation) (NN movement)) (ADVP (RB back) (NP (CD 20) (NNS years))))))
(ROOT (S (VP (VB ) (NP (NP (DT ) (NNS ) (POS )) (NN ) (NN )) (ADVP (RB ) (NP (CD ) (NNS ))))))