by Walter J. Wadsworth
Gemini Books, 2000
Buku Referensi
Koestenbaum, Peter
Jossey-Bass Publishers, 1991
Buku Teks
Burns, James McGregor
Harper and Row, 1978
Buku Teks
Glatthorn, Allan A.
Harper-Collins, 1987
Buku Teks
Yukl, Gary A., 1940-
Prentice-Hall, 1994
Buku Teks