S., A., B., A., H., S.(2009).Understanding and using English grammar: with answer key. Fourth Edition (dilengkapi CD) (Ed.Ke-4).:Pearson Education.
Gaya MLA
Azar, Betty, S.., Hagen, Stacy, A.."Understanding and using English grammar: with answer key. Fourth Edition (dilengkapi CD)".Ed.Ke-4:Pearson Education,2009.Textbook.