Gaya APA

Widiyanti, W., Maggs, M. (1978). Grolier English Programmed Course 4 (-). America: Grolier International, Inc.

Gaya MLA

Widiyanti, Wiwin., Maggs, Margaret. "Grolier English Programmed Course 4". - America: Grolier International, Inc, 1978. Text.