Morbidity among preschool children in Leningrad.
D002648:Child; D002675:Child, Preschool; D005260:Female; D006699:Home Care Services; D006760:Hospitalization; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D009017:Morbidity; D012140:Respiratory Tract Diseases / Q000453:epidemiology; D012959:Socioeconomic Factors; D014586:USSR