Cita APA (7th ed.)

Whitney, N. (1984). Checkpoint: English 1 (1a. ed.). Oxford University.

Cita Chicago (17th ed.)

Whitney, Norman. Checkpoint: English 1. 1a. ed. Oxford: Oxford University, 1984.

Cita MLA (9th ed.)

Whitney, Norman. Checkpoint: English 1. 1a. ed. Oxford University, 1984.