The New book of knowledge : volume 21
Grolier Incorporated, 1997
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The World book encyclopedia
World Book, 1992
Buku Referensi
The World book encyclopedia : volume 1
World Book, 1985
Buku Referensi
The World book encyclopedia : volume 2
World Book, 1985
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The World book encyclopedia : volume 3
World Book, 1985
Buku Referensi