Jenks, James M.
New Jersey : Alexander Hamilton Institute, Inc,
Buku Referensi
Randall S.Schuler, Susan E.Jackson, editor
Blackwell Publisher, 2000
Buku Teks
Chruden, Herbert J.
South-Western, 1966
Buku Teks
Ian Beardwell, Len Holden
Prentice-Hall, 2001
Buku Teks
Greer, Charles R., author
Prentice-Hall, 2001
Buku Teks