( However ( , ( ( most ( nitrogen oxides ) ) ( ( are ( ( formed ( by ( ( the reaction ) ( of ( atmospheric nitrogen ) ) ) ) ) ( with ( oxygen ( in ( high ( temperature flames ) ) ) ) ) ) ) . ) ) ) )
(ROOT (S (ADVP (RB However)) (, ,) (NP (JJS most) (NN nitrogen) (NNS oxides)) (VP (VBP are) (VP (VBN formed) (PP (IN by) (NP (NP (DT the) (NN reaction)) (PP (IN of) (NP (JJ atmospheric) (NN nitrogen))))) (PP (IN with) (NP (NP (NN oxygen)) (PP (IN in) (NP (JJ high) (NN temperature) (NNS flames))))))) (. .)))
However, most nitrogen oxides are formed by the reaction of atmospheric nitrogen with oxygen in high temperature flames.
(ROOT (S (NP (NNP Nitrogen)) (VP (VBZ oxide) (NP (NP (NN form)) (PRN (-LRB- -LRB-) (PRP s) (-RRB- -RRB-)) (SBAR (WHADVP (WRB when)) (S (NP (NN nitrogen) (CC and) (NN oxygen)) (VP (VBP combine) (PP (IN at) (NP (JJ high) (NNS temperatures)))))))) (. .)))