Trafton, P. R. (1989). New directions for elementary school mathematics. National Council of Teachers of Mathematics.
Citazione stile Chigago Style (17a edizione)Trafton, Paul R. New Directions for Elementary School Mathematics. Reston, Va.: National Council of Teachers of Mathematics, 1989.
Citatione MLA (8a ed.)Trafton, Paul R. New Directions for Elementary School Mathematics. National Council of Teachers of Mathematics, 1989.
Attenzione: Queste citazioni potrebbero non essere precise al 100%.