Cita APA

(1980). The billings method: A method of natural family planning. [Lugar de publicación no identificado]: Family of the Americas Foundations.

Citación estilo Chicago

The Billings Method: A Method of Natural Family Planning. [Lugar de publicación no identificado]: Family of the Americas Foundations, 1980.

Cita MLA

The Billings Method: A Method of Natural Family Planning. [Lugar de publicación no identificado]: Family of the Americas Foundations, 1980.