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المؤلفون: Caroline Hollingsworth, Lori Swensson, Donovan R. Lichtenberg, Shirley Fleitz, Christian R. Hirsch
المصدر: The Arithmetic Teacher. 37:2-56
المؤلفون: Caroline Hollingsworth, Lori Swensson, Donovan R. Lichtenberg, Shirley Fleitz, Christian R. Hirsch
المصدر: The Arithmetic Teacher. 37:2-56