1. Abnormale duur van de zwangerschap;Kloosterman,1981
2. Sociologic factors and birthweight in Great Britain;Alberman,1977
3. Project on preterm and small for gestational age infants in the Netherlands, 1983;Verloove-Vanhorick,1987
4. Perinatal intensive care: where and how to draw the line;Milligan;Am J Obstet Gynecol,1984
5. Prognosis for infants born at 23 to 28 weeks gestation;Yu;Br Med J,1986