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[2] INST HLTH CARLOS 3,MADRID,SPAIN
[3] WHO,CH-1211 GENEVA 27,SWITZERLAND
[4] HARVARD UNIV,SCH PUBL HLTH,BOSTON,MA 02115
[5] INST PASTEUR,F-75724 PARIS 15,FRANCE
[6] UNIV WISCONSIN,MCARDLE LAB CANC RES,MADISON,WI 53706
[7] NATL INST BIOL STAND & CONTROL,LONDON NW3 6RB,ENGLAND