Babcock, Chester D., author
Scott, Foresman, 1956
Buku Teks
Cuber, John F
Henry Holt And Company, 1951
Buku Teks
Farley, John E., author
Prentice-Hall, 1987
Buku Teks
Ferris, Brian, author
Hulton Educational Publications, 1973
Buku Teks
Arrow, Kenneth J., author
John Wiley & Sons, 1951
Buku Teks