Cole, J.P., author
Penguin Books, 1979
Buku Teks
edited by Frank Debenham
McGraw-Hill, 1960
Buku Referensi
United States. Central Intelligence Agency
Macmillan, 1993
Buku Referensi
Oxford University Press, 1972
Buku Referensi
foreword by Emrys Jones
Octopus Books, 1978
Buku Referensi