Não informado. (1973). Illinois school research and development. Illinois Association for Supervision and Curriculum Development.
Παραπομπή σε μορφή Chicago (17η εκδ.)Não informado. Illinois School Research and Development. Nottingham, Inglaterra: Illinois Association for Supervision and Curriculum Development, 1973.
Παραπομπή σε μορφή MLA (8th εκδ.)Não informado. Illinois School Research and Development. Illinois Association for Supervision and Curriculum Development, 1973.
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