Gaya APA

Betty, A, S., A., H, S. (2009). Understanding And Using English Grammar, Fourth Edition With Answer Key (Ke-4). USA: Pearson Education.

Gaya MLA

Betty, Azar, S.., A., Hagen, Stacy. "Understanding And Using English Grammar, Fourth Edition With Answer Key". Ke-4 USA: Pearson Education, 2009. PBI.