( ( Forms ( of energy ) ) ( ( include ( heat heat ) ) , ) )
(ROOT (S (NP (NP (NNS Forms)) (PP (IN of) (NP (NN energy)))) (VP (VBP include) (NP (NN heat) (NN heat))) (, ,)))
Forms of energy include heat heat,
(ROOT (S (NP (NNP Heat)) (VP (VBZ is) (VP (VBN produced) (SBAR (WHADVP (WRB when)) (S (NP (NN paper)) (VP (VBZ is) (VP (VBN burned))))))) (. .)))
Heat is produced when paper is burned.