1. The use of ultrasound in multiple gestations;Divers;Obstet Gynecol,1979
2. Simultaneous nonstress fetal heart rate testing in twin pregnancy;Devoe;Obstet Gynecol,1981
3. Significance of biparietal diameter. Differences between twins;Haney;Obstet Gynecol,1978
4. Growth discordancy in twin pregnancies: a risk factor not detected by measurements of biparietal diameter;Erkkola;Obstet Gynecol,1985
5. Accurate recording of twin placentation—a plea to obstetricians;Benirschke;Obstet Gynecol,1961