Gillespie, Cecil
Prentice-Hall, 1971
Buku Teks
Cousins, Donald
English Universities Press , 1955
Buku Teks
Niven, William
Prentice-Hall, 1964
Buku Teks
Joel G. Siegel
N.Y Barron, 1995
Buku Referensi
Warren, Carl S.
South-Western College, 1999
Buku Teks