Carey, John
Syracuse University Presss, 1971
Buku Teks SO
Abernathy, Charles F.
St. Paul Minn., 2000
Buku Teks
Sheridan, L.A.
Oceana Publications,Inc., 1963
Buku Teks
Emerson, Thomas I.
Little, Brown, 1981
Buku Teks SO
Abraham, Henry J.
Oxford University Press, 1982
Buku Teks SO