George, Jennifer M., author
Prentice Hall,, 2002
Buku Teks
Umstot, Denis D
West, 1984
Buku Teks
Schermerhorn, John R., author
John Wiley & Sons, 1991
Buku Teks
Moorhead, Gregory, author
South-Western Cengage Learning, 2012
Buku Teks
Barron, Robert A., author
Allyn and Bacon, 1990
Buku Teks