Cita APA (7th ed.)

Callen, P. W. (1988). Ultrasonography in obstetrics and Gynecology (2.ed.). Saunders Company.

Cita Chicago (17th ed.)

Callen, Peter W. Ultrasonography in Obstetrics and Gynecology. 2.ed. Philadelphia: Saunders Company, 1988.

Cita MLA (9th ed.)

Callen, Peter W. Ultrasonography in Obstetrics and Gynecology. 2.ed. Saunders Company, 1988.