1. J. B. DeLee, and J. P. Greenhill (1943 ): Principles and practice of obstetrics., 8th ed. Saunders, Philadelphia; p.673 .
2. J. B. DeLee, and J. P. Greenhill (1943 ): Principles and practice of obstetrics . 8th ed. Saunders, Philadelphia; p.672 .
3. The Elderly Primipara**Presented by invitation, at a meeting of the New York Obstetrical Society, January 11, 1944.