Variability in 28-day outcomes for very low birth weight infants: an analysis of 11 neonatal intensive care units. - Horbar,J.D.; McAuliffe,T.L.; Adler,S.M.; Albersheim,S.; Cassady,G.; Edwards,W.; Jones,R.; Kattwinkel,J.; Kraybill,E.N.; Krishnan,V. (Pediatrics, 1988)