Tohutoro APA (7th ed.)

Whitney, N. (1998). Open doors: Student's book + workbook. Oxford University Press.

Cita Chicago Style (17a ed.)

Whitney, Norman. Open Doors: Student's Book + Workbook. New York: Oxford University Press, 1998.

Cita MLA (9a ed.)

Whitney, Norman. Open Doors: Student's Book + Workbook. Oxford University Press, 1998.