(1989). Practice and reinforcement: (Blue level). New York: Mc Dougal, Littell & Company.
Stile di citazione ChicagoPractice and Reinforcement: (Blue Level). New York: Mc Dougal, Littell & Company, 1989.
Citazione MLAPractice and Reinforcement: (Blue Level). New York: Mc Dougal, Littell & Company, 1989.
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