Steinfels, Peter
Simon and Schuster, 1980
Buku Teks
Drucker, Peter F. (Peter Ferdinand), 1909-2005, author
Harper Colophan Books, 1977
Buku Teks
Hill, Christopher, author
Palbrave Macmillan, 2003
Buku Teks
Simmons, James C.
Harmony Books, 1990
Buku Teks
Oliveira, A. Ramos
Victor Gollancz Ltd., 1946
Buku Teks