Autor:	Rappaport, David, Stibal, Willard, Franson, Joseph P., Austin, Virginia Allen, Brekke, Gail, Young, Jerry L., Stettner, Christine, Porter, Fay A., Tunis, Harry B.
Zdroj:	The Arithmetic Teacher, 1981 Sep 01. 29(1), 2-54.
Databáze:	JSTOR Journals
Externí odkaz:	https://www.jstor.org/stable/41191967 Zobrazit plný text záznamu