R. Bennet et al. “Intestinal Bacteria of Newborn Ethiopian Infants in Relation to Antibiotic Treatment and Colonisation by Potentially Pathogenic Gram-Negative Bacteria”. Scandinavian Journal of Infectious Diseases 23, № 1 (1991); I. Adlerberth et al. “Intestinal Colonization with Enterobacteriaceae in Pakistani and Swedish Hospital-delivered Infants”. Acta Paediatrica Scandinavica 80, nos. 6–7 (1991).