Warner, Oliver
Longmans Green , 1958
Buku Teks
Wilson, John B., author
Longmans Green , 1958
Buku Teks
Evans, Ifor, Sir, author
Penguin Books, 1960
Buku Teks
Mulgan, John, author
Clarendon Press, 1967
Buku Teks
Lewis, Roy
Penguin Books, 1949
Buku Teks