[1] WHO,CH-1211 GENEVA 27,SWITZERLAND
[2] MIDDLESEX HOSP,SCH MED,BLAND SUTTON INST PATHOL,LONDON W1,ENGLAND
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[5] UNIV COPENHAGEN,HVIDOVRE HOSP,COPENHAGEN,DENMARK
[6] ROYAL FREE HOSP,SCH MED,LONDON NW3 2QG,ENGLAND