[1] MRC,EPIDEMIOL UNIT,CARDIFF,WALES
[2] KINGS COLL HOSP,MED SCH,DENMARK HILL,LONDON,ENGLAND
[3] UNIV LEEDS,DEPT PAEDIAT & CHILD HLTH,LEEDS,ENGLAND
[4] ROY HOSP SICK CHILDREN,YORKHILL,GLASGOW,SCOTLAND
[5] UNIV LONDON,THOMAS CORAM RES UNIT,LONDON,ENGLAND
[6] OFF POPULATION CENSUSES & SURVEYS,LONDON,ENGLAND
[7] ST BARTHOLOMEWS HOSP,MED UNIT,LONDON,ENGLAND
[8] BROMPTON HOSP,CARDIOTHORAC UNIT,LONDON,ENGLAND
[9] UNIV HOSP UPPSALA,DEPT PAEDIAT,UPPSALA,SWEDEN
[10] ST MARYS HOSP,MED SCH,PADDINGTON,LONDON,ENGLAND
[11] UNIV ROCHESTER,SCH MED,ROCHESTER,NY
[12] ENVIRONM HLTH DIRECTORATE CANADA,OTTAWA,ONTARIO,CANADA
[13] HOSP SICK CHILDREN,LONDON,ENGLAND