Gaya APA

PETERSEN, M, S., RIGBY, J, K. (1999). Interpreting earth history (6th ed.). United States of America: WCB McGraw-Hill.

Gaya MLA

PETERSEN, Morris, S.., RIGBY, J., Keith. "Interpreting earth history". 6th ed. United States of America: WCB McGraw-Hill, 1999. Text.