London Merlin Press 1994,
Buku Teks
Plamenatz, John
National News-Letter, 1949
Buku Teks
Sweezy, Paul M. (Paul Marlor), 1910-2004
McGraw-Hill, 1949
Buku Teks
Carr, Edward Hallet
Macmillan, 1950
Buku Teks
Gray, Alexander
Longmans, Green, 1948
Buku Teks SO