Kolevzon, Edward R., author
Allyn and Bacon, 1959
Buku Teks
James, Preston E., author
Macmillan, 1972
Buku Teks
by Les Rowntree ... [and others]
Prentice-Hall, 2011
Buku Teks
Cole, J.P., author
Penguin Books, 1979
Buku Teks
edited by Frank E. Bair
Gale Research Inc., 1991
Buku Referensi