Trafton, P. R. (1989). New directions for elementary school mathematics. National Council of Teachers of Mathematics.
Chicago-viite (17. p.)Trafton, Paul R. New Directions for Elementary School Mathematics. Reston, Va.: National Council of Teachers of Mathematics, 1989.
MLA-viite (8. p.)Trafton, Paul R. New Directions for Elementary School Mathematics. National Council of Teachers of Mathematics, 1989.
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