Asch, David, author
Crest Publishing House, 1999
Buku Referensi
Block, Stanley B., author
Irwin, 1994
Buku Teks
by Arthur J. Keown, John D. Martin, J. William Petty, David F. Scott
Prentice-Hall, 2001
Buku Teks
Prentice Hall International, 1991
Buku Teks
Madura, Jeff, author
Thomson South-Western, 2003
Buku Teks