Plamenatz, John
Longman Press, 1992
Buku Teks
Plamenatz, John
Longman Group Limited, 1963
Buku Teks
Germino, Dante L.
Rand McNally, 1972
Buku Teks
Carritt, E. F.
At The Clarendon Press, 1935
Buku Teks
Plamenatz, John
National News-Letter, 1949
Buku Teks