Pickle, Hal B.
Goodyear Publishing Company, Inc., 1972
Buku Teks
Kirkham, George L.
Harper & Row, Publishers, 1980
Buku Teks
Scott, William L.
Boston South-Western College Pub. 1999,
Buku Teks
Davis, Richard A.
Wm.C. Brown Publishers, 1991
Buku Teks
Babcock, Daniel L.
Prentice-Hall, 1991
Buku Teks