Clapham, John, Sir, author
University Press , 1944
Buku Teks
Larson, Laurence M., author
Holt , 1926
Buku Teks
edited by Albert C. Baugh
Appleton-Century-Crofts, 1948.
Buku Teks
Hall, Walter Phelps, author
Ginn and Company, 1953
Buku Teks
Churchill, Winston, Sir, 1874-1965, author
Wings Books, 1994
Buku Teks