Easton, David, author
John Wiley & Sons, 1965
Buku Teks
Easton, David, author
Knopf, 1971
Buku Teks
edited by Paul Boreham, Geoffrey Stokes and Richard Hall
Pearson-Longman, 2004
Buku Teks
Clinton, Richard L., author
Lexington Books, 1972
Buku Teks
Ebenstein, William, author
Rinehart, 1963
Buku Teks