Kirkpatrick, Colin H., author
George Allen and Unwin, 1984
Buku Teks
Johnson, Harry G., author
Praeger , 1968
Buku Teks
Eberstadt, Nick Ed.)
Praeger Publishers, 1981
Buku Teks
Bird, Graham
Macmillan, 1978
Buku Teks
Vance, Stanley C., author
Prentice-Hall, 1961
Buku Teks