Gaya APA

Lutgens, F. et al (2012). Essentials of Geology: Eleventh Edition (E-Book) . New Jersey: Pearson Prentice Hall.

Gaya MLA

Lutgens, Frederick. et al. "Essentials of Geology: Eleventh Edition (E-Book)". New Jersey: Pearson Prentice Hall, 2012. Text.