Foster, George M., author
Brown and Comp, 1969
Buku Teks
Kuper, Adam, author
Routledge, 1996
Buku Teks
Jennings, Jesse D., author
McGraw-Hill, 1972
Buku Teks
the Dushken Publishing, 1974
Buku Teks
Cole, Johnnetta B., author
The Free Press, 1982
Buku Teks