Some challenges to health services research on children and the elderly.
D000368:Aged; D002648:Child; D002662:Child Health Services; D006292:Health Priorities; D006293:Health Promotion; D006302:Health Services Research; D006299:Health Services for the Aged; D006801:Humans; D008962:Models, Theoretical; D011322:Primary Prevention; D012648:Self Care; D014481:United States