Gaya APA

AZAR, B, S., Hagen, S, A. (2009). Understanding And Using English Grammar: With Answer Key (4th ed.). New York: Pearson Longman.

Gaya MLA

AZAR, Betty, S.., Hagen, Stacy, A.. "Understanding And Using English Grammar: With Answer Key". 4th ed. New York: Pearson Longman, 2009. .