(S (S (BASENP (PRP He)) (VP (VBD postulated) (SBAR (IN that) (S (NP (BASENP (DT the) (NN source)) (PP (IN of) (BASENP (DT this) (NN energy)))) (VP (VBP are) (NP (BASENP (JJ thermonuclear) (NNS reactions)) (SBAR (WHPP (IN in) (WHNP (WDT which))) (S (BASENP (NN hydrogen)) (VP (VBD was) (VP (VBN converted) (PP (IN into) (BASENP (NN helium))))))))))))) (PERIOD .))