Sprague, Jo
Harcourt Brace College, 1996
Buku Teks
Douglas-Young, John
Parker Publishing Company, 1979
Buku Referensi
Ford Foundation, [date of publication not identified]
Buku Teks
Lindeman, Ralph D
Twayne Publishing, 1965
Buku Teks
Stroud, Angus, author
Routledge, 1999
Buku Teks