Routledge, 2000
Buku Teks
Taylor, Henry
New York A Mentore Books New American Library 1958,
Buku Teks
MacMillan St Martin's Press, 1953
Buku Referensi
Uldrich, Jack
[American Management Association, ], 2005
eBooks
edited by Brian Hunter
Macmillan, 1991
Buku Referensi