Gull, E.M.
The Royal Institute of International Affairs, 1947
Buku Teks
Mountford, James, Sir, author
Oxford Unniversity Press, 1966
Buku Teks
Stout, Hiram Miller, author
Oxford University Press, 1953
Buku Teks
Williams, Basil, author
Oxford University, 1945
Buku Klasik
Artikel Jurnal