Pence, Gregory E.
McGraw-Hill, 2000
Buku Teks
Heaton, J.B.
Longman, 1987
Buku Referensi
Goode, Walter
Cambridge University Press, 2007
Buku Referensi
Cuddon, J.A.
Penguin Books, 1979
Buku Referensi
Greenstein, Carol Horn
Van Nostrand Reinhold, 1978
Buku Referensi