Ballinger, Chris
United Kingdom Portland, Oregon Hart Publishing, 2012
Buku Teks
Jaceb, E. F., author
Clarendon Press, 1961
Buku Teks
Cook, Chris
Macmillan Press , 1984
Buku Teks
Cook, Chris
Macmillan Press , 1989
Buku Teks
Trevelyan, George Macaulay, 1876-1962, author
Longmans, Green, 1951
Buku Teks