( SULFUR ( TRIOXIDE . ) )
(ROOT (S (NP (NNP SULFUR)) (VP (VBP TRIOXIDE)) (. .)))
SULFUR TRIOXIDE .
(ROOT (S (NP (NNP Sulfur)) (VP (MD can) (VP (VB combine) (PP (IN with) (NP (NN oxygen))) (S (VP (TO to) (VP (VB produce) (NP (NN sulfur) (NN trioxide))))))) (. .)))