Fairhead, J. N.
English Universities Press, 1965
Buku Teks
Johnson, Rossall James, 1917-, author
South-Western Pub., 1970
Buku Teks
Mockler, Robert J., author
Prentice-Hall, 1989
Buku Teks
Miller, David W., author
Prentice-Hall, 1967
Buku Teks
Babson, Roger W., author
J.B. Lippincott, 1950
Buku Teks