1. Multiple pregnancy;Benirschke;N Engl J Med,1973
2. Multiple pregnancy;Benirschke;N Engl J Med,1973
3. The Developing Human;Moore,1982
4. The Pathology of the Human Placenta;Benirschke,1967
5. Twin placenta in perinatal mortality;Benirschke;NY State J Med,1961