Sutherland, Max, author
PPM, 2004
Buku Teks
Sutherland, Max, author
Allen and Unwin, 2000
Buku Teks
Hotchkiss, George Burton, author
Alexander Hamilton Institute , 1961
Buku Teks
Wells, William D., author
Prentice-Hall, 2000
Buku Teks
Weilbacher, William M
Macmillan, 1979
Buku Teks