Roper, Kathy O.
American Management Association, 2014
Buku Teks
Pyzdek, Thomas
McGraw-Hill, 2003
Buku Referensi
Booher, Diana
Prentice-Hall, 1991
Buku Teks
Fopp, Michael A.
Routledge, 1997
Buku Teks
Shepherd, Elizabeth J., 1960-
London, Facet
Buku Referensi