Bowles, Chester, author
Harper, 1955
Buku Teks
Steel, Ronald
The VIking Press, 1968
Buku Teks
Dulles, John Foster
Macmillan Company, 1950
Buku Teks
Bowles, Chester, author
Harper & Brothers, 1958
Buku Teks
Gray, Colin S., author
Simon & Schuster, 1990
Buku Teks