Langdon, Robert M.
Littlefield Adams, 1961
Buku Teks
Bisson, T.A.
Macmilan Co., 1945
Buku Teks
Leopold, Richard W.
Alfred A. Knopf, 1962
Buku Teks
Pratt, Julius W.
Prentice-Hall, 1965
Buku Teks
London, Kurt, editor
D.van Nostrand Company,Inc., 1950
Buku Teks