( ( ( ( -LSB- NOTE ) : ) ( PAHs ( are ( ( a group ) ( of ( ( chemicals ( that ( are ( formed ( during ( ( the ( incomplete burning ) ) ( of ( ( ( coal ( , ( oil ( , ( gas ( , ( wood ( , ( garbage , ) ) ) ) ) ) ) ) ) or ) ( other ( organic substances ) ) ) ) ) ) ) ) ) ) ( -LRB- ( 22 -RRB- ) ) ) ) ) ) ) ) . )
(ROOT (NP (NP (JJ -LSB-) (NN NOTE)) (: :) (S (NP (NNP PAHs)) (VP (VBP are) (NP (NP (DT a) (NN group)) (PP (IN of) (NP (NP (NNS chemicals)) (SBAR (WHNP (WDT that)) (S (VP (VBP are) (VP (VBN formed) (PP (IN during) (NP (NP (DT the) (JJ incomplete) (NN burning)) (PP (IN of) (NP (NP (NN coal) (, ,) (NN oil) (, ,) (NN gas) (, ,) (NN wood) (, ,) (NN garbage) (, ,)) (CC or) (NP (JJ other) (JJ organic) (NNS substances)))))))))) (PRN (-LRB- -LRB-) (NP (CD 22)) (-RRB- -RRB-))))))) (. .)))
[NOTE: PAHs are a group of chemicals that are formed during the incomplete burning of coal, oil, gas, wood, garbage, or other organic substances ( 22 ).
(ROOT (S (NP (NNP Wood) (NNP burning)) (VP (VBZ is) (NP (NP (DT an) (NN example)) (PP (IN of) (NP (NP (DT a) (JJ different) (NN substance)) (VP (VBG being) (VP (VBN formed))))))) (. .)))