Autor:	Martin, Hope, Stokes, Betty, Tracy, Dyanne M., Woodward, Ernie, Gibbs, Virginia, Proske, Cindy Lafitte, Melter, Robert A., Ott, Jack, Currence, Jerry, Kinard, Amelia
Zdroj:	The Arithmetic Teacher, 1989 Oct 01. 37(2), 2-47.
Databáze:	JSTOR Journals
Externí odkaz:	https://www.jstor.org/stable/41193746 Zobrazit plný text záznamu