Gaya APA

Azar, B, S., Hagen, S, A. (2009). Understanding and Using English Grammar Fourth Edition With Answer Key (Ed. 4). USA: Pearson Longman.

Gaya MLA

Azar, Betty, Schrampfer., Hagen, Stacy, A.. "Understanding and Using English Grammar Fourth Edition With Answer Key". Ed. 4 USA: Pearson Longman, 2009. Text.