Billings, E., & Westmore, A. (1980). The Billings method of Natural Family Planning: Controlling fertility without drugs or devices (1st American ed.). Random House.
Dyfyniad Arddull ChicagoBillings, Evelyn, and Ann Westmore. The Billings Method of Natural Family Planning: Controlling Fertility Without Drugs or Devices. 1st American ed. New York: Random House, 1980.
Dyfyniad MLABillings, Evelyn, and Ann Westmore. The Billings Method of Natural Family Planning: Controlling Fertility Without Drugs or Devices. 1st American ed. Random House, 1980.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.