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NATIONAL ACADEMY PRESS 



The National Academy Press was created by 

 the National Academy of Sciences to publish 

 the reports issued by the Academy and by the 

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 of Medicine, and the National Research Council, 

 all operating under the charter granted to the 

 National Academy of Sciences by the Congress 

 of the United Sutes. 



ISBN D-3D'1-QS3M7-L 

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9"780309"053471 



