Morgan, Theodore, author
Prentice-Hall, 1950
Buku Teks
Cairncross, Alec, author
Butterworth, 1960
Buku Teks
Johnson, Alvin S., author
Hearh & Co., 1911
Buku Teks
Hailstones, Thomas J., author
South-Western Publishing, 1974
Buku Teks
Chang, Semoon, author
Allyn and Bacon, 1990
Buku Teks