(1989). Practice and reinforcement: (Blue level). New York: Mc Dougal, Littell & Company.
Chicago Style CitationPractice and Reinforcement: (Blue Level). New York: Mc Dougal, Littell & Company, 1989.
Cita MLAPractice and Reinforcement: (Blue Level). New York: Mc Dougal, Littell & Company, 1989.
Atenció: Aquestes cites poden no estar 100% correctes.