The psychology of algebra - Thorndike, Edward L. (Edward Lee), 1874-1949.; Cobb, Margaret V. (Margaret Vara), b. 1884.; Orleans, Jacob S. (Jacob Samuel), 1899-; Symonds, Percival Mallon, 1893-; Wald, Elva.; Woodyard, Ella, b. 1878. (The Macmillan company, 1923)