`` `` the cases consisted of a sample of infant deaths which were registered at the registry office and which occurred in the metropolitan region of porto alegre ( brazil ) in 1980 , and the control group was a sample of births occurring in the same region in 1980 , and also notified to the registry office . with information obtained from a special household survey , a total of 688 cases and 762 controls [ were ] analyzed ... for maternal education and its association with family income , birth order and environmental factors . specific relative risks ( associated with maternal education ) have also been calculated separately for 3 groups of cause-of-death and for 3 age-at-death groups . '' ''
C0549159
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C0011065
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