Low, H.V.
Longman, 1967
Buku Teks
Kenyon, Anne E.
Prentice-Hall, 1969
Buku Teks
Washington, Allyn J., author
Cummings Menlo Park, 1969
Buku Teks
Devine, Donald F., author
John Wiley & Sons, 1983
Buku Teks
Heckenbach, Alan J., author
Macmillan, 1970
Buku Teks