(S (S (S (PP (VBG According) (PP (TO to) (BASENP (NNS demonstrators)))) (S (NP (EX there)) (VP (VBD were) (BASENP (NN 500,000) (NNS people))))) (COMMA ,) (SBAR (IN while) (S (BASENP (DT the) (NNP Police)) (VP (VBZ estimates) (NP (BASENP (DT a) (NN turnout)) (PP (IN of) (BASENP (NN 200,000)))))))) (PERIOD .))