(S (S (BASENP (NNP Poland)) (VP (VBZ has) (VP (VP (VBN declared) (NP (BASENP (DT a) (NN week)) (PP (IN of) (BASENP (JJ national) (NN mourning))))) (PP (IN after) (BASENP (DT the) (NN incident)))))) (PERIOD .))