Huebner, S. S., author
Appleton Century Crofts, 1972
Buku Teks
Black, Kenneth, author
Prentice-Hall, 1994
Buku Teks
Huebner, S. S., author
Appleton-Century Crafts, 1958
Buku Teks
Magee, John H.
Richard D. Irwin, 1951
Buku Teks
R & R Newkirk/Longman, 1985
Buku Referensi