Bloom, Gordon F.
Irwin , 1969
Buku Teks
McEachern, William A., author
South-Western College Publishing, 1988
Buku Teks
edited by Howard S. Elllis
Blakiston, 1949
Buku Teks
Flanagan, Robert J.
Scott, Foresman, 1984
Buku Teks
Reynolds, Lloyd G., author
Prentice-Hall, 1982
Buku Teks