Gaya APA
Spong, C, Y. et al (2010).
WILLIAMS OBSTETRICS 23RD EDITION (23rd edition).
United states of America:
McGraw-Hill Book Company.
Gaya MLA
Spong, Catherine, Y.. et al.
"WILLIAMS OBSTETRICS 23RD EDITION".
23rd edition
United states of America:
McGraw-Hill Book Company,
2010.
Text.