Raed, Jane M.
Chandos Publishing, 2003
Buku Teks
Callahan, Robert E.
Merrill , 1988
Buku Teks
Drucker, Peter Ferdinand, 1909-2005
Truman Talley Books/Plume, 1992
Buku Teks
Chattell, Alf
Macmillan, 1995
Buku Teks
Barbeito, Carol L.
John wiley & sons, inc, 2004
Buku Teks