(S (S (NP (BASENP (NNP Pentagon) (NN spokesman) (NNP Bryan) (NNP Whitman)) (COMMA ,)) (VP (VBD acknowledged) (SBAR (IN that) (S (BASENP (NNS allegations)) (VP (VP (VBD were) (VP (VBN made) (PP (IN on) (QT (DQL ``) (BASENP (JJ rare) (NNS occasions)) (DQR ''))))) (CC but) (VP (VBD were) (VP (VBN uncorroborated)))))))) (PERIOD .))