Cita APA (7a ed.)

Billings, E., & Westmore, A. (1981). The Billings method: Controlling fertility without drugs or devices. Allen Lane.

Cita Chicago Style (17a ed.)

Billings, Evelyn, y Ann Westmore. The Billings Method: Controlling Fertility Without Drugs or Devices. London: Allen Lane, 1981.

Cita MLA (9a ed.)

Billings, Evelyn, y Ann Westmore. The Billings Method: Controlling Fertility Without Drugs or Devices. Allen Lane, 1981.