[1] HAMMERSMITH HOSP,ROYAL POSTGRAD MED SCH,DEPT SURG,DU CANE RD,LONDON W12 0NN,ENGLAND
[2] ROYAL FREE HOSP,SCH MED,DEPT SURG,LONDON NW3 2QG,ENGLAND
[3] ROYAL FREE HOSP,SCH MED,DEPT MED,LONDON NW3 2QG,ENGLAND
[4] UNIV LONDON UNIV COLL,DEPT GENET & BIOMETRY,LONDON NW1 2HE,ENGLAND