Morrison, Charles E., author
Martin Press, 1978
Buku Teks
Jones, Joseph Marion
Macmillan, 1944
Buku Teks
Westview press 1985, 1982
Buku Teks
Northrop, F. S. C., author
Macmillan, 1954
Buku Teks
Mangone, Gerard J.
Syracuse University Press, 1962
Buku Teks