(S (S (PP (VBG According) (PP (TO to) (BASENP (NNP Lewis) (NNP PR)))) (COMMA ,) (S (NP (BASENP (NNS computers)) (PP (IN on) (BASENP (DT the) (JJ main) (NNP MoD) (NNS networks)))) (VP (VBP are) (VP (VBN blocked) (PP (IN from) (S (VP (VBG visiting) (BASENP (JJ social) (NN networking) (NNS sites))))))))) (PERIOD .))