The New book of knowledge : volume 21
Grolier Incorporated, 1997
 Buku Referensi
The World book encyclopedia
World Book, 1992
 Buku Referensi
The World book encyclopedia : volume 1, A
Field Enterprises Educational Corporation, 1963
 Buku Referensi
The World book encyclopedia : volume 16, S
Field Enterprises Educational Corporation, 1963
 Buku Referensi
The World book encyclopedia : volume 17, T
Field Enterprises Educational Corporation, 1963
 Buku Referensi