1. Hirnes, M. E.: Medical History of Contraception. p. 137. New York, Gamut Press, 1936 (reprinted 1963).
2. Johnston, R. D.: The history of human infertility. Fertil. Steril. 14, 266, 1963.
3. As 1: p. 141.
4. Avicenna: Libri V Canonis medicinae. Sect. iii, tract. II, cap. XXI. Romae, typ, Medicae, 1593.
5. Avicenna: Canon Avicennae. III, 118, ed. 1294. Bulak, 1877.