Dumont, Raymond A., author
Little, Brown, 1985
Buku Teks
Woolcott, Lysbeth A., author
Erlangga, 1990
Buku Teks
Wilson, Kevin, author
American Management Association, 2010
eBooks
Merriam-Webster, Inc., 1988
Buku Teks
Lesikar, Raymond V. (Raymond Vincent), author
McGraw-Hill/Irwin , 2002
Buku Teks