(S (S (NP (BASENP (NNS Hundreds)) (PP (IN of) (BASENP (NNS people)))) (VP (VBP are) (VP (VBN believed) (S (VP (TO to) (VP (VB have) (VP (VBN died) (PP (IN as) (NP (BASENP (DT a) (NN result)) (PP (IN of) (BASENP (DT these) (NNS experiments)))))))))))) (PERIOD .))