Unger, Maurice A., author
Allyn and Bacon, 1969
Buku Teks
Dauten, Carl Anton, 1913-, author
Prentice-Hall, 1948
Buku Teks
edited by Carl S. Shoup
Aldine Publishing, 1969
Buku Teks
Knox, David M., author
McGraw-Hill, 1990
Buku Teks
Cissell, Robert, author
Houghton Mifflin, 1964
Buku Teks