among three strands which allow us to view events as if through a prism 
(ROOT (PP (IN among) (NP (NP (CD three) (NNS strands)) (SBAR (WHNP (WDT which)) (S (VP (VBP allow) (S (NP (PRP us)) (VP (TO to) (VP (VB view) (NP (NNS events)) (SBAR (IN as) (IN if) (FRAG (PP (IN through) (NP (DT a) (NN prism))))))))))))))
(ROOT (PP (IN ) (NP (NP (CD ) (NNS )) (SBAR (WHNP (WDT )) (S (VP (VBP ) (S (NP (PRP )) (VP (TO ) (VP (VB ) (NP (NNS )) (SBAR (IN ) (IN ) (FRAG (PP (IN ) (NP (DT ) (NN ))))))))))))))