Philip's illustrated encyclopedia / editors: Chris Humphries, Steve Luck, Frances Adlington
George Philip Limited, 1999
Buku Referensi
The encyclopedia American
Americana Corporation, 1980
Buku Referensi
The Columbia encyclopedia
Columbia University Press, 1950
Buku Referensi
The encyclopedia Americana
Americana corporation, 1938
Buku Referensi
The encyclopedia American
Americana Corporation, 1980
Buku Referensi