Wortabet, John, author
Frederick Ungar Publishing, 1954
Buku Referensi
Elias, Elias A., author
Elias Modern Press, 1972
Buku Referensi
Dickins, James, author
Routledge, 2002
Buku Teks
Macmillan, 1948
Buku Teks
Martin, James, author
Prentice-Hall, 1989
Buku Teks