Gaya APA
Norton, M, E. et al (2017).
Callen's Ultrasonography in Obstetrics and Gynecology, 6th ed. (6th. Ed).
Philadelphia:
Elsevier.
Gaya MLA
Norton, Mary, E. et al.
"Callen's Ultrasonography in Obstetrics and Gynecology, 6th ed.".
6th. Ed
Philadelphia:
Elsevier,
2017.
Text.