Meyer, Harold E., author
Prentice-Hall, 1992
Buku Referensi
Seglin, Jeffrey L., author
Amacom, 1996
Buku Referensi
edited by L. Edward Purcell
Prentice-Hall, 1991
Buku Referensi
Wilson, Kevin, author
American Management Association, 2010
eBooks
Merriam-Webster, Inc., 1988
Buku Teks