Cornog, Mary Wood
Springfield:Massachusetts Merriam-Webster, 1994,
Buku Teks
New York : Holt, Rinehart and Winston, 1995,
Buku Teks
Harahap, P.R.
Jakarta Praninta Aksara [date of publication not identified],
Buku Teks
Holschuh, Louis W.
New York St. Martin's Press 1991,
Buku Teks
Hughes, John
London Collins 1994,
Buku Teks