Skees, William D.
Lifetime Learning Publications, 1982
Buku Teks
Van Duyn, Julia, author
John Wiley & Sons, 1982
Buku Referensi
edited by Edward Barrett
MIT Press, 1988
Buku Teks
Gallagher, James D.
American Management Association, 1961
Buku Teks
Spencer, Donald D., author
Prentice-Hall, 1974
Buku Referensi