Billings, E., & Westmore, A. (1980). The Billings method of Natural Family Planning: Controlling fertility without drugs or devices (1st American ed.). Random House.
芝加哥风格引文Billings, Evelyn, 与 Ann Westmore. The Billings Method of Natural Family Planning: Controlling Fertility Without Drugs or Devices. 1st American ed. New York: Random House, 1980.
MLA引文Billings, Evelyn, 与 Ann Westmore. The Billings Method of Natural Family Planning: Controlling Fertility Without Drugs or Devices. 1st American ed. Random House, 1980.
警告：这些引文格式不一定是100％准确.