(S (S (BASENP (NNS Doctors)) (VP (VBD were) (ADJP (JJ unaware) (SBAR (IN if) (S (BASENP (PRP he)) (VP (VBZ knew) (SBAR (IN that) (S (BASENP (PRPD his) (NN wife)) (VP (VP (VBD did) (RB not)) (VP (VB survive) (BASENP (DT the) (NN attack)))))))))))) (PERIOD .))