(S (S (BASENP (JJ Duplicate) (NNS books)) (VP (VBP are) (VP (VP (VBN required) (PP (IN for) (BASENP (DT the) (JJ individual) (NN four) (NNS camps)))) (S (VP (TO to) (VP (VB prevent) (NP (NP (BASENP (JJ covert) (NN use)) (PP (IN of) (BASENP (NNS books)))) (S (VP (TO to) (VP (VB communicate) (PP (IN between) (BASENP (NNS camps))))))))))))) (PERIOD .))