National Council of Teachers of Mathematics & Trafton, P. R. (1989). New directions for elementary school mathematics. NCTM.
Citazione stile Chigago Style (17a edizione)National Council of Teachers of Mathematics e Paul R. Trafton. New Directions for Elementary School Mathematics. Reston, VA: NCTM, 1989.
Citatione MLA (9a ed.)National Council of Teachers of Mathematics e Paul R. Trafton. New Directions for Elementary School Mathematics. NCTM, 1989.
Attenzione: Queste citazioni potrebbero non essere precise al 100%.