Seligman, Eustace, author
New York University Press, 1956.
Buku Teks
Katcher, Bruce Leslie, author
American Management Association, 2007
eBooks
Sigman, Aric, author
London, 2005
Buku Teks
Hacker, Andrew , author
St. Martin's Griffin, 2011
Buku Teks
Farrell, Warren, author
[American Management Association, ], 2005
eBooks