gathering dust on mgm 's shelf 
(ROOT (S (VP (VBG gathering) (NP (NN dust)) (PP (IN on) (NP (NP (NNP mgm) (POS 's)) (NN shelf))))))
(ROOT (S (VP (VBG ) (NP (NN )) (PP (IN ) (NP (NP (NNP ) (POS )) (NN ))))))