(S (S (BASENP (DT The) (NNS researchers)) (VP (VBD reported) (SBAR (IN that) (S (BASENP (DT these) (NNS kidneys)) (VP (VP (VBD produced) (BASENP (NN urine))) (PP (IN at) (NP (BASENP (NN 23) (NN %)) (PP (IN of) (NP (BASENP (DT the) (JJ normal) (NNS levels)) (PP (IN of) (NP (VP (ADVP (RB properly)) (VBG working)) (NNS kidneys)))))))))))) (PERIOD .))