Philips
Chancellor Press, 1999
Buku Referensi
McNally, Rand
Rand McNally & Co, 1957
Buku Referensi
edited for the Society of American Historians by Courtlandt Canby & Nancy E. Gross
New American Library, 1954
Buku Teks SO
Revill, J.C.
Longman, 1959
Buku Teks SO
Dorling Kindersley, 1998
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