Kornblum, William, author
Wadsworth and Cengage Learning, 2012
Buku Teks
Kornblum, William, author
Harcourt Brace College Publishers, 1997
Buku Teks
Bryjak, George J
Allyn and Bacon, 1994
Buku Teks
Schrag, Clarence C., author
Harper & Row, 1963
Buku Teks
Zanden, James W. Vander, author
John Wiley & Sons, 1979
Buku Teks