Hansen, Don R., author
South-Western College Publishing, 1997
Buku Teks
Usry, Milton F., author
South Western, 1988
Buku Teks
Gillespie, Cecil, author
Prentice-Hall, 1957
Buku Teks
Dopson, Lea R.
John Wiley & Son, 2008
Multimedia
Hansen, Don R., author
South-Western College Publishing, 1997
Buku Teks