(S (S (S (NP (BASENP (NNP Singh)) (PRN (COMMA ,) (BASENP (DT a) (NN diabetic)) (COMMA ,))) (VP (VP (VP (VBD underwent) (BASENP (DT a) (NN bypass) (NN surgery))) (PP (IN in) (BASENP (NNP Britain)))) (PP (IN in) (BASENP (NN 1990))))) (CC and) (S (S (VP (VP (VP (VBD had) (BASENP (DT an) (NN angioplasty))) (PP (IN in) (BASENP (NN 2004)))) (PP (IN in) (BASENP (NNP Delhi))))) (SBAR (WHPP (IN in) (WHNP (WDT which))) (S (BASENP (NNS stents)) (VP (VBD were) (VP (VBN introduced) (PP (IN in) (BASENP (PRPD his) (NNS arteries))))))))) (PERIOD .))