(S (S (NP (BASENP (JJ Such) (JJ inadvertent) (NN overdosing)) (PRN (COMMA ,) (SINV (VP (VBP say)) (BASENP (DT the) (NNS researchers))) (COMMA ,))) (VP (VBZ has) (VP (VBN contributed) (PP (TO to) (NP (BASENP (NN controversy)) (PP (IN over) (NP (BASENP (NN melatonin) (POS 's)) (NN efficacy)))))))) (PERIOD .))