Farmer, Neil
John Wiley & Sons, 1996
Buku Teks
Griffin, Ricky W.
Pearson Education International, 2006
Buku Teks
Griffin, Ricky W.
Prentice-Hall, 1999
Buku Teks
Griffin, Ricky W.
Prentice-Hall, 2002
Buku Teks
Wheeler, Bayard O.
Harper & Row. Publisher, 1968
Buku Teks