(S (S (BASENP (DT The) (NNPS Navy)) (VP (PRN (COMMA ,) (ADVP (RB however)) (COMMA ,)) (VP (VBD had) (NP (NP (BASENP (DT no) (NN knowledge)) (PP (IN of) (BASENP (PDT such) (DT an) (NN exercise)))) (CONJP (COMMA ,) (CC and)) (NP (BASENP (DT no) (NNS reports)) (PP (IN from) (NP (BASENP (JJ other) (NNS nations)) (PP (VBG regarding) (BASENP (DT the) (NN submarine)))))))))) (PERIOD .))