Martin, Mearle, author
Prentice-Hall, 2003
Buku Teks
Romney, Marshall B., author
Prentice-Hall, 2003
Buku Teks
Bodnar, George H., author
Prentice-Hall, 1998
Buku Referensi
Gelinas, Ulric J., author
South-Western , 2005
Buku Teks
Summers, Edward Lee, author
Houghton Mifflin, 1989
Buku Teks