(S (S (BASENP (JJ Several) (JJ senior) (JJ Russian) (NNS politicians)) (VP (VP (VBP have) (VP (VBN said) (SBAR (IN that) (S (NP (BASENP (DT the) (NNS deaths)) (PP (IN of) (BASENP (NNP Politkovskaya) (CC and) (NNP Litvinenko)))) (VP (VBD were) (VP (VBG playing) (PP (IN into) (NP (BASENP (DT the) (NNS hands)) (PP (IN of) (NP (BASENP (NNP Russia) (POS 's)) (NNS enemies))))))))))) (CONJP (CC and) (COMMA ,)) (VP (ADVP (RB therefore)) (COMMA ,) (VP (VP (MD could) (RB not)) (VP (VB have) (VP (VBN been) (VP (VBN authorized) (PP (IN by) (BASENP (NNP Moscow)))))))))) (PERIOD .))