Cita APA

(1987). Practice and reinforcement: (Purple level). New York: McDougal, Littell & Companay.

Chicago Style Citation

Practice and Reinforcement: (Purple Level). New York: McDougal, Littell & Companay, 1987.

Cita MLA

Practice and Reinforcement: (Purple Level). New York: McDougal, Littell & Companay, 1987.

Atenció: Aquestes cites poden no estar 100% correctes.