Papp, Daniel S., author
Macmillan, 1984
Buku Teks
Papp, Daniel S., author
Allyn and Bacon, 1997
Buku Teks
Papp, Daniel S., author
Macmillan, 1988
Buku Teks
Jones, Walter S.
Harper Collins , 1991
Buku Teks
Couloumbis, Theodore A., author
Prentice-Hall, 1990
Buku Teks