Egbert, Richard T.
Prentice-Hall, 1991
Buku Referensi
Roper, Kathy O., author
American Management Association, 2014
Buku Teks
Pyzdek, Thomas, author
McGraw-Hill, 2003
Buku Referensi
Booher, Diana
Prentice-Hall, 1991
Buku Teks
Fopp, Michael A., author
Routledge, 1997
Buku Teks