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[New York] Random House 1968 .
ix, 189 p. 23 cm..

By Pratt, Fletcher.
Garden City, N.Y. Blue Ribbon Books 1942 .
282 p.

By Ball, W. W. Rouse.
London The Macmillan company 1931 .
xiii, 366 p., 1 l. 21 cm..

By Ball, W. W. Rouse.
London The MacMillan Company 1940 .
xvi, 418 p., 1 l.

By Peck, Lyman C..
Washington National Council of Teachers of Mathematics 1961 .
54 p.