1. Aladjem, S.: The early placentastructure and function. 3rd Internat. Conference on congenital Malformations, Den Haag 1969
2. Arey, L. B.: Developmental anatomy. A textbook and laboratory manual of embryology. Phila delphiaLondon: Saunders Comp. 1965
3. Asling, C. W.: Nutrition and teratogenesis. In: Methods for teratological studies in experimental animals and men. Tokyo: Igaku Shoin Ltd. 1969
4. Becker, V.: Die Placenta bei der Geburt. Fortschr. Med. 4, 132 (1969)
5. Berendes, H.: The NIH collaborative study — a progress report. 3rd Internat. Conference on congenital Malformations, Den Haag 1969