McPhee, John
Farrar, Straus and Giroux, 1966
Buku Teks
Stover, Vergil G.
Prentica-Hall, 1988
Buku Teks
Baum, lawrence
A Division of Congressional Quarterly Inc, 1989
Buku Teks
Greenhut, Melvin L.
Prentice-Hall, 1961
Buku Teks
Frank, William W.
Macmillan, 1959
Buku Teks