American Journal of Epidemiology Copyright O 1999 by The Johns Hopkins University School of Hygiene and Public Health All rights reserved Vol. 149, No. 2 Printed In U.SA.

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		American Journal of Epidemiology Copyright O 1999 by The Johns Hopkins University School of Hygiene and Public Health All rights reserved Vol. 149, No. 2 Printed In U.SA. Add to Reading List Source URL: aje.oxfordjournals.org Download Document from Source Website File Size: 712,86 KB Share Document on Facebook