Clarkson, Donald R.
The Shoe String Press, 1964
Buku Teks
Kenyon, Anne E.
Prentice-Hall, 1969
Buku Teks
McFarland, Dora
Mass. Heath , 1968
Buku Teks
Armstrong, James W., author
Macmillan, 1976
Buku Teks
Campbell, Hugh G., author
Macmillan, 1974
Buku Teks