Edward, David V.
Prentice-Hall, 1982
Buku Teks
Penniman, Howard R., author
D. Van Nostrand, 1962
Buku Teks
Kendall, Willmoore, author
Louisiana University Press, 1970
Buku Teks
Plano, Jack C., author
Holt, Rinehart and Winston, 1985
Buku Referensi
Good, Yohn M
Heath, 1970
Buku Teks