The World book encyclopedia : volume 4
World Book, 1985
 Buku Referensi
The New book of knowledge : volume 8
Grolier Incorporated, 1997
 Buku Referensi
The New book of knowledge : volume 9
Grolier Incorporated, 1997
 Buku Referensi
The New book of knowledge : volume 10
Grolier Incorporated, 1997
 Buku Referensi
The New book of knowledge : volume 11
Grolier Incorporated, 1997
 Buku Referensi