Fitzhugh, K., & Fitzhugh, L. (1966). Fitzhugh PLUS program: Perceptual learning and understanding skills. Allied Educational Council.
Lua i Stíl Chicago (17ú heag.)Fitzhugh, Kathleen, agus Loren Fitzhugh. Fitzhugh PLUS Program: Perceptual Learning and Understanding Skills. Galien, Mich.: Allied Educational Council, 1966.
Lua MLA (8ú heag.)Fitzhugh, Kathleen, agus Loren Fitzhugh. Fitzhugh PLUS Program: Perceptual Learning and Understanding Skills. Allied Educational Council, 1966.
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