(S (S (BASENP (DT This) (NN announcement)) (VP (VBD was) (VP (VP (VBN followed) (ADVP (BASENP (NN two) (NNS days)) (RBR later))) (PP (IN by) (NP (BASENP (NNP NASDAQ) (NN ®)) (COMMA ,) (SBAR (WHNP (WDT which)) (S (ADVP (RB independently)) (VP (VBD announced) (NP (BASENP (DT a) (JJ definitive) (NN agreement)) (S (VP (TO to) (VP (VB purchase) (BASENP (NNP Instinet) (NNP Group)))))))))))))) (PERIOD .))