Smith, Elliott L., author
St. Martin's Press, 1994
Buku Teks
Green, George S.
Holt, Rinehart and Winston, 1972
Buku Teks
Fowler, H. W. (Henry Watson), 1858-1933, author
Oxford University Press, 1965
Buku Referensi
Mager, N. H., author
Prentice-Hall, 1975
Buku Referensi
Peters, Pam, author
Cambridge University Press, 2006
Buku Referensi