Boyd, William E., author
Prentice-Hall, 1955
Buku Teks
Magee, John H.
Irwin , 1969
Buku Teks
Bruce D. Mudget [and others]
Alexander Hamilton Institute, 1962
Buku Teks
Williams, Numan A., author
South-Western Publicashing, 1984
Buku Teks
Dinsdale, W.A.
Sir Isaac Pitman & Sons, Ltd. , 1959
Buku Teks