Garrison, Ray H.,
Irwin, 1997
Buku Teks
Knapp, Michael C., author
Ohio South-Western, 1998
Buku Teks
DeCoster, Don T., author
Melville Publishing Company, 1974
Buku Teks
Ingram, Robert W., author
Thomson/South-Western, 2004
Multimedia
Killough, Larry N., author
Dickenson Publishing, 1977
Buku Teks