(S (S (ADVP (RB However)) (COMMA ,) (S (NP (NP (BASENP (DT the) (NN complexity)) (PP (IN of) (BASENP (DT the) (NN data) (NN analysis)))) (PP (IN along) (PP (IN with) (BASENP (JJ unforeseen) (NN engineering) (NNS problems))))) (VP (VBP have) (VP (VBN made) (S (S (VP (VP (VBG finding) (BASENP (DT the) (NN effect))) (PP (IN in) (NP (BASENP (DT the) (NN experiment) (POS 's)) (NNS results))))) (ADJP (JJ difficult))))))) (PERIOD .))