Wells, William D.
John Wiley & Sons, 1996
Buku Teks SO
Schiffman, Leon G.
Pearson Education International, 2004
Buku Teks SO
Engel, James F.
Chicago Dryden Press, 1990
Buku Teks SO
Mowen, John C.
Macmillan, 1987
Buku Teks SO
Schiffman, Leon G.
Prentice-Hall, 1997
Buku Teks