Parekh, H. T.
Oxford University Press, 1953
Buku Teks
Auerbach, Robert D., author
Macmillan, 1989
Buku Teks
Stigum, Marcia
Illinois Dow Jones- Irwin , 1983
Buku Teks
Dufei, Gunter, author
Prentice-Hall, 1978
Buku Teks
Burgess, W. Randolph
Harper & Brothers , 1946
Buku Teks