Relative Difficulty of the One Hundred Multiplication Facts with Special Reference to Textbook Construction

Autor:	Ruch, G. M.
Zdroj:	The Elementary School Journal, 1932 Jan 01. 32(5), 369-377.
Databáze:	JSTOR Journals
Externí odkaz:	https://www.jstor.org/stable/995927 Zobrazit plný text záznamu