Easton, David, author
New York, N. Y. Wiley 1967,
Buku Teks
Easton, David, author
Prentice-Hall, 1965
Buku Teks
Easton, David, author
John Wiley & Sons, 1965
Buku Teks
Butler, David
Radius Book/ Hutchinson, 1970
Buku Teks
Cohen, Barry
Pinguin Bokks, 1989
Buku Teks