1. Baxi PG. A natural history of childbearing in the hospital class of women in Bombay. J Obstet Gynecol India 1957;8:26–51.
2. Dandekar K. Demographic Survey of Six Rural Communities. Poona: Gokhale Institute of Politics and Economics, 1959, p. 62.
3. Davis ME. The clinical use of oral basal temperatures. JAMA 1946;130:929–932.
4. Ehrenfest H. Reappearance of menstruation after childbirth. Am J Obstet Dis Women Child 1915;72:577–599.
5. Elsner P. Erste Menstruation nach Partus und Abortus. Weiner Klinische Wochenschrift 1948;60:433–435.