The New Encyclopaedia Britannica : volume 17, macropaedia knowledge in depth
Encyclopaedia Britannica Inc., 1998
 Buku Referensi
The New Encyclopaedia Britannica : volume 15, macropaedia knowledge in depth
Encyclopaedia Britannica Inc., 1998
 Buku Referensi
The New encyclopaedia Britannica : volume 24, macropaedia knowledge in depth
Encyclopaedia Britannica Inc., 1998
 Buku Referensi
The New encyclopaedia Britannica : volume 26, macropaedia knowledge in depth
Encyclopaedia Britannica Inc., 1998
 Buku Referensi
The New encyclopaedia Britannica : volume 27, macropaedia knowledge in depth
Encyclopaedia Britannica Inc., 1998
 Buku Referensi