Heddens, J. W. (1974). Today's mathematics: A guide to concepts and methods in elementary school mathematics. Science Research Associates.
Παραπομπή σε μορφή Chicago (17η εκδ.)Heddens, James W. Today's Mathematics: A Guide to Concepts and Methods in Elementary School Mathematics. Chicago, IL: Science Research Associates, 1974.
Παραπομπή σε μορφή MLA (9th εκδ.)Heddens, James W. Today's Mathematics: A Guide to Concepts and Methods in Elementary School Mathematics. Science Research Associates, 1974.
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