(S (S (S (NP (BASENP (DT The) (JJ 41st) (NN anniversary)) (PP (IN of) (BASENP (DT the) (NNP Apollo) (NN 1) (NN fire)))) (VP (VBD was) (PP (IN on) (BASENP (NNP Sunday))))) (CONJP (COMMA ,) (CC and)) (S (BASENP (NNP Monday)) (VP (VBD saw) (NP (BASENP (DT the) (JJ 22nd) (NN anniversary)) (PP (IN of) (BASENP (DT the) (NNP Challenger) (NN disaster))))))) (PERIOD .))