Rutherford, Donald
Routledge, 1992
Buku Referensi
Bannock, G.
Penguin Books, 1974
Buku Referensi
Bannock, G.
Allen Lane / The Viking Press, 1979
Buku Referensi
general editor, David W. Pearce
Macmillan Reference Books, 1989
Buku Referensi
general editor, David W. Pearce
Macmillan Press, 1992
Buku Referensi