Cita APA (7th ed.)

Whitney, N. (1998). Open doors 1A: Student's book + workbook. Oxford University Press.

Cita Chicago (17th ed.)

Whitney, Norman. Open Doors 1A: Student's Book + Workbook. New York: Oxford University Press, 1998.

Cita MLA (9th ed.)

Whitney, Norman. Open Doors 1A: Student's Book + Workbook. Oxford University Press, 1998.